If anyone can help I'd appreciate it:

I'm trying to troubleshoot a Cosmec CNC Machining Center that runs a NUM 1020M PLC. I have found a few specific resources for this machine, but not as many people run it because it is so outdated. But, I am trying to figure out what PLC logic command is keeping the relay for the CNC motor from turning on (or closing). It had been working, but a setting change or configuration change has caused the relay not to work when powering up the machine. Initially, the communications from the computer to the machine was interrupted, but now the communication is working. It goes through the RS232 serial port via COM1.

My belief is that the problem occurred due to a voltage drop which has been happening when a large compressor kicks on which has been resulting in a Digital Servo Fault causing the WatchDog to turn on. Usually, it is possible to just power off the machine and power it back up and the fault is corrected without either interrupting the communications or the ability to power up the machine, but something has occurred which is now keeping the CNC from being powered on when turning on the machine.

Can someone tell me what the standard logic input commands would be that would block the CNC from powering up? The have found no LEDs that indicate any components are inoperable. It doesn't appear any of the fuses are blown and the general configuration settings of the machine itself have not been knowingly altered. There are multiple inputs on the machine, but I wouldn't think all of them would cause the machine not to power up, but to display an error message. Any assistance would be appreciated.