When the coach is plugged in or on the generator you're getting 12VDC from the converter. The problem could be a couple of things.
First double and triple check your battery configuration particularly if you are using multiple batteries and since you have new batteries. If everything worked before the new batteries were installed then check what was the last thing touched. Easy to connect them incorrectly if it isn't something you do everyday.
Next thing to try is the Aux Start switch with the coach unplugged and the generator off. Just turn on a convenient ceiling light and press the switch. If the light comes that confirm the storage or house battery disconnect set to distribute power to the house. I could be wrong on this one though. If will depend on how the DC power distribution network was designed.
Next check the if you have a large amperage fuse between the batteries and the distribution network. You could also have a circuit breaker rather than a fuse that needs reset.
Tells us what you find or if the suggestions don't help.
2006 Hurricane 31D built on a 2006 Ford F53