this sounds more than strange. I would understand if you do not see any nodes anymore... but if you only see the OPs... do the OPs connect to the PLCs on MPI? If so, do they see the CPUs?

I do not know, have you checked the wiring yet? Have you checked if you maybe see something with another MPI capable device on the Network? May you tell me also which MPI Address the PC has? (usually it is 0)

I hope we will find a solution.

Best regards