Mitsubishi A2SHCPU

I have a Mitsubishi A2SHCPU that has an error LED on. I cannot reset this and have tried to go online to the PLC to see if I can reset it, but I keep getting a communication error. Using the exact same connection settings, I can go online to another PLC in the station next to the one I am working on, verifying my hardware and settings are good. I ordered a replacement PLC and installed it. I still get the same error as I had with the old one, and the same comm error. I have zero experience with Mitsubishi PLCs. Can someone tell me another step to take? I have been in contact with Mitusubishi with no real help.

are you using an SC09 red cable to connect?

Have you tried closing all the device/batch monitor screens, (if they are opened) and then re attempt to communicate. In the past if I have a device/batch monitor screen open from the last session, it would not let me in. (the comms option was greyed out). Hope this helps regards Badger.

Yes, I am using the red cable. I don't have any batch or monitor screens open.
I swapped the PLC out of working machine to the one i am working on and I can't communicate with that PLC with my pc or the HMI. Last night, I swapped the PLC, HMI, and cable to the non-working machine and could not communicate. I put the non-working PLC and put it in the 2nd machines rack and I could establish communication, but would get a time out error when i tried to read from PLC. This made me think i might have a bad rack, so this morning I took the rack from the working machine and swapped it. Using the station's original PLC, HMI and cables, and the problem remained the same. My error is gone on the PLC now but communication still cannot be established. I had purchased a new (surplus), PLC and it is giving the same symtoms.

did you try changing the power supply as it may be the back plan of the Power supply 5v DC rail that is the cause.
the comms need the 5 volt supply
it may also be the back plane connections