This might sound basic, but confirm your shore power line, whatever kind you are using, is hot. I originally plugged my geopro into an outdoor outlet that was GFCI. The GFCI on that outlet popped I think, and i was scratching my head wondering why i had no power. If your microwave display is lit, you are getting power into the trailer.
Another thing is if you use a EMS. It will not supply power for a couple of minutes after you plug it in, it is designed that way.
The OP has a small travel trailer, so no such thing as an Onan built-in generator.[emoji1786]Check onan Jenny breaker