Ok as a test, can you make sure all is clear so you are cutting air. Go to Config, Ports and Pins then Inputs and enable the emulated for the index and then set a keyboard key for it, maybe the F1. Run the code and if it stops at the threading then start pressing the F1 key as fast as you can and see if it starts threading.
Regarding the LED on the prox and LED in Mach, no thats just the screen cant refresh fast enough to see it.
Oh one more thing, maybe your axis cant move fast enough for the spindle speed in the code and the pitch, maybe try editing the spindle speed to 300 instead of the 1000.
Hood