Probe Basic ATC Setup Problems

It might be helpful to turn on debugging in terminal to see exactly what point in the sequence its getting stuck.

INI file
[DISPLAY]
DEBUG = 0x10

And then start LCNC from the terminal.

Attempt your tool change (M6 T1 or T1 M6) and when it gets hung up, use ALT-TAB to switch to the terminal window.  You should be able to see what commands are going on in LCNC and likely a hint as to exactly what is hanging up.

I agree with spumco, run in terminal so the debug messages show the failure point. Probably something simple I had 0 where an o word should have been that chased for 2 days troubleshooting.. probably started at it 50 times and that was with debug on telling me where the problem was

Maybe post your toolchange sub also

I reply into this because I had the same problem and solved it (thanks to Crish as always for the help) you probably are not calling tool prepared, or something iocontrol.x.tool related that "hangs" the toolchange

In my case was something like calling M64P7 with:
net ATC-pocket-reached motion.digital-out-07 iocontrol.0.tool-prepared

happy to help and glad you got it sorted out!