I had the same problem where my batteries would charge but the inverter would not work and I couldn't get the inside panel to do anything.
I tried turning on the inverter on the unit itself and nothing happened. I was about to take it out and replace when I started messing around with it a little more. I found out that you have to hold the power button down on the inverter for 5-10 seconds before it would turn on, not just press and release. Mime fortunately did turn on then.
I decided it was probably just a bad remote controller inside the coach. I removed it and ran a short cord (just an old phone line cord) from the unit inside the bay to the control panel and it worked! So in my case it is a bad cord and I just need to run a new one.
Hopefully yours is this simple or this information helps someone else in the future