Make sure that you have setup highlighted when you Post Process. Or the actual operation you want to make into a gcode file. You can use any or all of the operations you want.
Also it has to spit out 4 numbers first I think.
1001 and so on.
I always just add the file name after that prenumbered sequence.
Works great.
Oh and the Post is Haas (pre NGC)
New Mini Mill with umbrella changer.
Not sure what the difference might be for an NGC post. I haven't seen one to try.