HAI Omni pro expansion 17a00

I had one in place, came down and noticed it was dead. Unplugged, replaced battery, power supply. When I plugged in seem to start up ok, then the status started flashing rapidly. Then the system shut down.

Purchased a new board, same thing happened. If I do not connect the data then the board does not shut down.

What could be wrong?

If this is the ONLY expansion you have on the bus then you need to look at the OMNI, but if you have other things on the bus (locks, keypads, etc) then unhook everything else just have the OMNI and the 17A00 and see if it still has a problem? If not, start adding things back in until it goes tits up and then you know where to look. The RS485 bus can be a bitch to diagnose sometimes especially when it has lots of stuff on it. 

Thanks for replying. I have two expansions boxes. This card is connected to the relay board. When I disconnected from this, the card does at least stay on. The setup has been working for the past 12 years without any issues. What can cause the expansion board to shut down?

Is everything else (other expansion board, keypads) working ok, even if the faulty expansion board shuts down?