ECN Forum Forums General Topics of the Trade General Discussion Area Solid State Relays and electrical isolation

Let's step back and start from the beginning.
1) system worked at some time in the past.
2) system stopped working.
3) Someone replaced relay board three times until system started working again.
4) You replaced relay on relay board, tested it on a test fixture, which said relay board is OK. Relay board was installed in system and system does not work.

Is this the sequence of events?