Also, have you looked at every receptacle in and around the RV for GFCI's? Ours has one on the outside under the awning and one inside in the bath.
If that doesn't solve the problem, I'd start pulling the receptacles to see if there was a wire that came lose behind one of them. I've seen that happen before.
Salem 29RKSS Pushing a 2500 Mega-Cab CTD!
Gotta go campin!