If you have checked as follows:
1.DC power every output voltage
2.air break on or ff
3.CNC board has any alarm is lighted
4.servo unite has alarm.

If above is ok i suggest you display top part of pmc. normally top part of pmc is EMG button and Feedhold button.

you can check emg button and feedhold button diagnostic information.

You can also check overtravel limited switch signal by pmc.

Because EMG & overtravel signal are fix address in PMC.

If these signal are good or not good you can use a voltage signal (+24V or 0v) directly connecting socket pin of pmc.

if your pmc is running you will show some activities of PMC.