Only half my electrical outlets work

You may want to check for an additional GFCI device in back of the fridge, in the bathroom, under/over the kitchen counter, or on the exterior of the trailer (near an outside kitchen).

Did you check the ckt breaker on the inverter? Some of your ckts run through the inverter, not the main breaker panel.

Um, yes, I turned the breakers on/off (sorry I wasn't more explicit when I said I checked them). I've searched high and low for a second GFCI...haven't found one...so I guess my next thing is to check for the loose wires, specifically on the outlets I'm having trouble with. Thanks...I was afraid I had to do that, although it's much better for ME to do that than to have to pay an astronomical price to someone else to do the same thing.

Moved from Forum Technical Support

When you 'checked all my breakers...everything seemed fine'--how did you check them?

Did you turn them to OFF and then reset back to ON?

Also.......check the wires on breaker and make sure they are tight/making good contact.

And you might look around for another GFCI outlet.....check if tripped.

Tripped GFCIs, tripped circuit breakers, loose wire on breaker AND one other possibility.
A loose wire in an outlet upstream of those that aren't working. Requires identifying the suspect outlet....pulling it and checking the wires for proper connections.
RV outlets are cheap design.....they use a split-prong that the wires clip/push into vs hardwired/screwed or even a good push contact like residential outlets.

They wire the outlets in a daisy chain string..if wire works loose (easy to do) then all outlets downstream stop working.