Problem with Posting G-code with Fusion 360

Looks like your grbl.cps is messed up, did you edit it at all?

Here's my config. When you hit post process, click 'Open config' next to the configuration dropdown and paste this in the editor. Save and try exporting again, it should save as a .nc file.

Spoiler: grbl.cps

/**
Copyright (C) 2012-2016 by Autodesk, Inc.
All rights reserved.

Carbide 3D Grbl post processor configuration.

$Revision: 40938 a817b859e9f28db15a5b2095f1122568118223e4 $
$Date: 2016-01-15 19:38:05 $
FORKID {154F7C00-6549-4c77-ADE0-79375FE5F2AA}
*/

description = "Generic Carbide 3D (Grbl)";
vendor = "Carbide 3D";
vendorUrl = "Carbide 3D";
legal = "Copyright (C) 2012-2016 by Autodesk, Inc.";
certificationLevel = 2;
minimumRevision = 24000;

extension = "nc";
setCodePage("ascii");

capabilities = CAPABILITY_MILLING;
tolerance = spatial(0.002, MM);

minimumChordLength = spatial(0.01, MM);
minimumCircularRadius = spatial(0.01, MM);
maximumCircularRadius = spatial(1000, MM);
minimumCircularSweep = toRad(0.01);
maximumCircularSweep = toRad(180);
allowHelicalMoves = true;
allowedCircularPlanes = undefined; // allow any circular motion



// user-defined properties
properties = {
writeMachine: true, // write machine
writeTools: true, // writes the tools
showSequenceNumbers: false, // show sequence numbers
sequenceNumberStart: 10, // first sequence number
sequenceNumberIncrement: 1, // increment for sequence numbers
separateWordsWithSpace: true // specifies that the words should be separated with a white space
};

var numberOfToolSlots = 9999;



var mapCoolantTable = new Table(
[9, 7],
{initial:COOLANT_OFF, force:true},
"Invalid coolant mode"
);

var gFormat = createFormat({prefix:"G", decimals:0});
var mFormat = createFormat({prefix:"M", decimals:0});

var xyzFormat = createFormat({decimalsunit == MM ? 3 : 4)});
var feedFormat = createFormat({decimalsunit == MM ? 1 : 2)});
var toolFormat = createFormat({decimals:0});
var rpmFormat = createFormat({decimals:0});
var secFormat = createFormat({decimals:3, forceDecimal:true}); // seconds - range 0.001-1000
var taperFormat = createFormat({decimals:1, scaleEG});

var xOutput = createVariable({prefix:"X"}, xyzFormat);
var yOutput = createVariable({prefix:"Y"}, xyzFormat);
var zOutput = createVariable({prefix:"Z"}, xyzFormat);
var feedOutput = createVariable({prefix:"F"}, feedFormat);
var sOutput = createVariable({prefix:"S", force:true}, rpmFormat);

// circular output
var iOutput = createReferenceVariable({prefix:"I", force:true}, xyzFormat);
var jOutput = createReferenceVariable({prefix:"J", force:true}, xyzFormat);
var kOutput = createReferenceVariable({prefix:"K", force:true}, xyzFormat);

var gMotionModal = createModal({}, gFormat); // modal group 1 // G0-G3, ...
var gPlaneModal = createModal({onchange:function () {gMotionModal.reset();}}, gFormat); // modal group 2 // G17-19
var gAbsIncModal = createModal({}, gFormat); // modal group 3 // G90-91
var gUnitModal = createModal({}, gFormat); // modal group 6 // G20-21

var WARNING_WORK_OFFSET = 0;

// collected state
var sequenceNumber;
var currentWorkOffset;

/**
Writes the specified block.
*/
function writeBlock() {
if (properties.showSequenceNumbers) {
writeWords2("N" + sequenceNumber, arguments);
sequenceNumber += properties.sequenceNumberIncrement;
} else {
writeWords(arguments);
}
}

function formatComment(text) {
return "(" + String(text).replace(/[\(\)]/g, "") + ")";
}

/**
Output a comment.
*/
function writeComment(text) {
writeln(formatComment(text));
}

function onOpen() {
if (!properties.separateWordsWithSpace) {
setWordSeparator("");
}

sequenceNumber = properties.sequenceNumberStart;
writeln("%");

if (programName) {
writeComment(programName);
}
if (programComment) {
writeComment(programComment);
}

// dump machine configuration
var vendor = machineConfiguration.getVendor();
var model = machineConfiguration.getModel();
var description = machineConfiguration.getDescription();

if (properties.writeMachine && (vendor || model || description)) {
writeComment(localize("Machine"));
if (vendor) {
writeComment(" " + localize("vendor") + ": " + vendor);
}
if (model) {
writeComment(" " + localize("model") + ": " + model);
}
if (description) {
writeComment(" " + localize("description") + ": " + description);
}
}

// dump tool information
if (properties.writeTools) {
var zRanges = {};
if (is3D()) {
var numberOfSections = getNumberOfSections();
for (var i = 0; i < numberOfSections; ++i) {
var section = getSection(i);
var zRange = section.getGlobalZRange();
var tool = section.getTool();
if (zRanges[tool.number]) {
zRanges[tool.number].expandToRange(zRange);
} else {
zRanges[tool.number] = zRange;
}
}
}

var tools = getToolTable();
if (tools.getNumberOfTools() > 0) {
for (var i = 0; i < tools.getNumberOfTools(); ++i) {
var tool = tools.getTool(i);
var comment = "T" + toolFormat.format(tool.number) + " " +
"D=" + xyzFormat.format(tool.diameter) + " " +
localize("CR") + "=" + xyzFormat.format(tool.cornerRadius);
if ((tool.taperAngle > 0) && (tool.taperAngle < Math.PI)) {
comment += " " + localize("TAPER") + "=" + taperFormat.format(tool.taperAngle) + localize("deg");
}
if (zRanges[tool.number]) {
comment += " - " + localize("ZMIN") + "=" + xyzFormat.format(zRanges[tool.number].getMinimum());
}
comment += " - " + getToolTypeName(tool.type);
writeComment(comment);
}
}
}

// absolute coordinates and feed per min
writeBlock(gAbsIncModal.format(90));
writeBlock(gPlaneModal.format(17));

switch (unit) {
case IN:
writeBlock(gUnitModal.format(20));
break;
case MM:
writeBlock(gUnitModal.format(21));
break;
}
}

function onComment(message) {
writeComment(message);
}

/** Force output of X, Y, and Z. */
function forceXYZ() {
xOutput.reset();
yOutput.reset();
zOutput.reset();
}

/** Force output of X, Y, Z, and F on next output. */
function forceAny() {
forceXYZ();
feedOutput.reset();
}

function onSection() {
var insertToolCall = isFirstSection() ||
currentSection.getForceToolChange && currentSection.getForceToolChange() ||
(tool.number != getPreviousSection().getTool().number);
var retracted = false; // specifies that the tool has been retracted to the safe plane
var newWorkOffset = isFirstSection() ||
(getPreviousSection().workOffset != currentSection.workOffset); // work offset changes
var newWorkPlane = isFirstSection() ||
!isSameDirection(getPreviousSection().getGlobalFinalToolAxis(), currentSection.getGlobalInitialToolAxis());
if (insertToolCall || newWorkOffset || newWorkPlane) {

// stop spindle before retract during tool change
if (insertToolCall && !isFirstSection()) {
onCommand(COMMAND_STOP_SPINDLE);
}

// retract to safe plane
retracted = true;
writeBlock(gFormat.format(28), gAbsIncModal.format(91), "Z" + xyzFormat.format(0)); // retract
writeBlock(gAbsIncModal.format(90));
zOutput.reset();
}

writeln("");
if (hasParameter("operation-comment")) {
var comment = getParameter("operation-comment");
if (comment) {
writeComment(comment);
}
}

if (insertToolCall) {
retracted = true;
onCommand(COMMAND_COOLANT_OFF);

if (tool.number > numberOfToolSlots) {
warning(localize("Tool number exceeds maximum value."));
}

writeBlock("T" + toolFormat.format(tool.number), mFormat.format(6));
if (tool.comment) {
writeComment(tool.comment);
}
var showToolZMin = false;
if (showToolZMin) {
if (is3D()) {
var numberOfSections = getNumberOfSections();
var zRange = currentSection.getGlobalZRange();
var number = tool.number;
for (var i = currentSection.getId() + 1; i < numberOfSections; ++i) {
var section = getSection(i);
if (section.getTool().number != number) {
break;
}
zRange.expandToRange(section.getGlobalZRange());
}
writeComment(localize("ZMIN") + "=" + zRange.getMinimum());
}
}
}
if (insertToolCall ||
isFirstSection() ||
(rpmFormat.areDifferent(tool.spindleRPM, sOutput.getCurrent())) ||
(tool.clockwise != getPreviousSection().getTool().clockwise)) {
if (tool.spindleRPM < 1) {
error(localize("Spindle speed out of range."));
}
if (tool.spindleRPM > 99999) {
warning(localize("Spindle speed exceeds maximum value."));
}
writeBlock(
sOutput.format(tool.spindleRPM), mFormat.format(tool.clockwise ? 3 : 4)
);
}

// wcs
if (insertToolCall) { // force work offset when changing tool
currentWorkOffset = undefined;
}
var workOffset = currentSection.workOffset;
if (workOffset == 0) {
warningOnce(localize("Work offset has not been specified. Using G54 as WCS."), WARNING_WORK_OFFSET);
workOffset = 1;
}
if (workOffset > 0) {
if (workOffset > 6) {
error(localize("Work offset out of range."));
return;
} else {
if (workOffset != currentWorkOffset) {
writeBlock(gFormat.format(53 + workOffset)); // G54->G59
currentWorkOffset = workOffset;
}
}
}

forceXYZ();

{ // pure 3D
var remaining = currentSection.workPlane;
if (!isSameDirection(remaining.forward, new Vector(0, 0, 1))) {
error(localize("Tool orientation is not supported."));
return;
}
setRotation(remaining);
}

// set coolant after we have positioned at Z
{
var c = mapCoolantTable.lookup(tool.coolant);
if (c) {
writeBlock(mFormat.format(c));
} else {
warning(localize("Coolant not supported."));
}
}

forceAny();

var initialPosition = getFramePosition(currentSection.getInitialPosition());
if (!retracted) {
if (getCurrentPosition().z < initialPosition.z) {
writeBlock(gMotionModal.format(0), zOutput.format(initialPosition.z));
}
}

if (insertToolCall || retracted) {
var lengthOffset = tool.lengthOffset;
if (lengthOffset > numberOfToolSlots) {
error(localize("Length offset out of range."));
return;
}

gMotionModal.reset();
writeBlock(gPlaneModal.format(17));

if (!machineConfiguration.isHeadConfiguration()) {
writeBlock(
gAbsIncModal.format(90),
gMotionModal.format(0), xOutput.format(initialPosition.x), yOutput.format(initialPosition.y)
);
writeBlock(gMotionModal.format(0), zOutput.format(initialPosition.z));
} else {
writeBlock(
gAbsIncModal.format(90),
gMotionModal.format(0),
xOutput.format(initialPosition.x),
yOutput.format(initialPosition.y),
zOutput.format(initialPosition.z)
);
}
} else {
writeBlock(
gAbsIncModal.format(90),
gMotionModal.format(0),
xOutput.format(initialPosition.x),
yOutput.format(initialPosition.y)
);
}
}

function onDwell(seconds) {
if (seconds > 99999.999) {
warning(localize("Dwelling time is out of range."));
}
seconds = clamp(0.001, seconds, 99999.999);
writeBlock(gFormat.format(4), "P" + secFormat.format(seconds));
}

function onSpindleSpeed(spindleSpeed) {
writeBlock(sOutput.format(spindleSpeed));
}

var pendingRadiusCompensation = -1;

function onRadiusCompensation() {
pendingRadiusCompensation = radiusCompensation;
}

function onRapid(_x, _y, _z) {
var x = xOutput.format(_x);
var y = yOutput.format(_y);
var z = zOutput.format(_z);
if (x || y || z) {
if (pendingRadiusCompensation >= 0) {
error(localize("Radius compensation mode cannot be changed at rapid traversal."));
return;
}
writeBlock(gMotionModal.format(0), x, y, z);
feedOutput.reset();
}
}

function onLinear(_x, _y, _z, feed) {
// at least one axis is required
if (pendingRadiusCompensation >= 0) {
// ensure that we end at desired position when compensation is turned off
xOutput.reset();
yOutput.reset();
}
var x = xOutput.format(_x);
var y = yOutput.format(_y);
var z = zOutput.format(_z);
var f = feedOutput.format(feed);
if (x || y || z) {
if (pendingRadiusCompensation >= 0) {
error(localize("Radius compensation mode is not supported."));
return;
} else {
writeBlock(gMotionModal.format(1), x, y, z, f);
}
} else if (f) {
if (getNextRecord().isMotion()) { // try not to output feed without motion
feedOutput.reset(); // force feed on next line
} else {
writeBlock(gMotionModal.format(1), f);
}
}
}

function onRapid5D(_x, _y, _z, _a, _b, _c) {
error(localize("Multi-axis motion is not supported."));
}

function onLinear5D(_x, _y, _z, _a, _b, _c, feed) {
error(localize("Multi-axis motion is not supported."));
}

function onCircular(clockwise, cx, cy, cz, x, y, z, feed) {
// one of X/Y and I/J are required and likewise
if (pendingRadiusCompensation >= 0) {
error(localize("Radius compensation cannot be activated/deactivated for a circular move."));
return;
}

var start = getCurrentPosition();

if (isFullCircle()) {
if (isHelical()) {
linearize(tolerance);
return;
}
// TAG: are 360deg arcs supported
switch (getCircularPlane()) {
case PLANE_XY:
writeBlock(gPlaneModal.format(17), gMotionModal.format(clockwise ? 2 : 3), xOutput.format(x), iOutput.format(cx - start.x, 0), jOutput.format(cy - start.y, 0), feedOutput.format(feed));
break;
case PLANE_ZX:
writeBlock(gPlaneModal.format(18), gMotionModal.format(clockwise ? 2 : 3), zOutput.format(z), iOutput.format(cx - start.x, 0), kOutput.format(cz - start.z, 0), feedOutput.format(feed));
break;
case PLANE_YZ:
writeBlock(gPlaneModal.format(19), gMotionModal.format(clockwise ? 2 : 3), yOutput.format(y), jOutput.format(cy - start.y, 0), kOutput.format(cz - start.z, 0), feedOutput.format(feed));
break;
default:
linearize(tolerance);
}
} else {
switch (getCircularPlane()) {
case PLANE_XY:
writeBlock(gPlaneModal.format(17), gMotionModal.format(clockwise ? 2 : 3), xOutput.format(x), yOutput.format(y), zOutput.format(z), iOutput.format(cx - start.x, 0), jOutput.format(cy - start.y, 0), feedOutput.format(feed));
break;
case PLANE_ZX:
writeBlock(gPlaneModal.format(18), gMotionModal.format(clockwise ? 2 : 3), xOutput.format(x), yOutput.format(y), zOutput.format(z), iOutput.format(cx - start.x, 0), kOutput.format(cz - start.z, 0), feedOutput.format(feed));
break;
case PLANE_YZ:
writeBlock(gPlaneModal.format(19), gMotionModal.format(clockwise ? 2 : 3), xOutput.format(x), yOutput.format(y), zOutput.format(z), jOutput.format(cy - start.y, 0), kOutput.format(cz - start.z, 0), feedOutput.format(feed));
break;
default:
linearize(tolerance);
}
}
}

var mapCommand = {
COMMAND_STOP:0,
COMMAND_END:2,
COMMAND_SPINDLE_CLOCKWISE:3,
COMMAND_SPINDLE_COUNTERCLOCKWISE:4,
COMMAND_STOP_SPINDLE:5,
COMMAND_COOLANT_ON:7,
COMMAND_COOLANT_OFF:9
};

function onCommand(command) {
switch (command) {
case COMMAND_START_SPINDLE:
onCommand(tool.clockwise ? COMMAND_SPINDLE_CLOCKWISE : COMMAND_SPINDLE_COUNTERCLOCKWISE);
return;
case COMMAND_LOCK_MULTI_AXIS:
return;
case COMMAND_UNLOCK_MULTI_AXIS:
return;
case COMMAND_BREAK_CONTROL:
return;
case COMMAND_TOOL_MEASURE:
return;
}

var stringId = getCommandStringId(command);
var mcode = mapCommand[stringId];
if (mcode != undefined) {
writeBlock(mFormat.format(mcode));
} else {
onUnsupportedCommand(command);
}
}

function onSectionEnd() {
writeBlock(gPlaneModal.format(17));
forceAny();
}

function onClose() {
onCommand(COMMAND_COOLANT_OFF);

writeBlock(gFormat.format(28), gAbsIncModal.format(91), "Z" + xyzFormat.format(0)); // retract
zOutput.reset();

if (!machineConfiguration.hasHomePositionX() && !machineConfiguration.hasHomePositionY()) {
writeBlock(gFormat.format(28), gAbsIncModal.format(91), "X" + xyzFormat.format(0), "Y" + xyzFormat.format(0)); // return to home
} else {
/* // G53 is not supported
var homeX;
if (machineConfiguration.hasHomePositionX()) {
homeX = "X" + xyzFormat.format(machineConfiguration.getHomePositionX());
}
var homeY;
if (machineConfiguration.hasHomePositionY()) {
homeY = "Y" + xyzFormat.format(machineConfiguration.getHomePositionY());
}
writeBlock(gAbsIncModal.format(90), gFormat.format(53), gMotionModal.format(0), homeX, homeY);
*/
}

onImpliedCommand(COMMAND_END);
onImpliedCommand(COMMAND_STOP_SPINDLE);
writeBlock(mFormat.format(30)); // stop program, spindle stop, coolant off
writeln("%");
}

If that doesnt work I would reinstall F360, mine had issues with cam processing when I first installed it.
Just a quick helpful tip, setup a g28 position before running your cam or delete those lines in the gcode file. It took me forever to figure out why my machine ran into the endstops when I ran the files. Just move to a position high above your workspace and send g28.1.

 

I missed that bit. Check your tool paths to see if you've changed your tool orientation at all, it should be under the heights tab for each tool path you created.