Over the years I've had a few OBi20x devices just crap out on me. I've taken them apart and haven't seen anything visual to indicate the problem, but they get power, but that's about it. They are just dead. I keep a couple of spares laying around for myself or customers/friends, just in case.
You're best bet is to just order another one. I've spent hours in the past troubleshooting and experimenting. In my experience, once what you're describing happens, there's nothing you can do.
Sorry.