This is what they found with the Inverter:
Found that a Fuse was blown, and the fan was not working. Both needing to be replaced.
He also found when he opened it up that an insulator sheet was missing, which protects the Circuit board from metal.
Hopefully this fixes it. It was not original to the RV and had been replaced but I am sure the previous owner didn't look into getting if fixed. Will keep advice above just in case. It was working fined on shore power at my home and when we traveled before we started having issues.