There will be a very large fuse between the battery bank and the inverter input. Should be anyway. That's how I would wire it. That will be on the 12V side of the thing.
It will look like this:
High Amperage Inverter Fuses & Breakers
I'm assuming a coach will have something like this. But this will only explain why the inverter isn't inverting. It will not explain why the bypass circuitry isn't working. There should be a breaker on your AC panel for the inverter. This breaker provides power to the inverter when you are connected to shore power and trips the bypass in the inverter to send 110V AC on through to the circuits connected to the inverter. On the other side of the inverter there will be breakers to the outlets that are provided inverted power.
So no inversion: large fuse on the AC side.
No power downstream of the inverter when plugged into shore power, breaker problem feeding the inverter, the inverter bypass (inside the inverter so nothing to be done about that) or the breakers on the output side of the inverter.
Pardon any ignorance of how large coaches are wired. I haven't seen any of those. Yet.