Old-Biscuit gave you a starting point, from resetting all the CBs, remove panel and check the output of each CB. Don't forget checking the GFCI locations by pushing the test and then reset. It is sometimes hard to tell if a CB of GFCI has been tripped that is why when we changed all the outlets and wall switches in our S&B, I installed GFCIs with indicator lights.
This is a good point to recommend that you label all your CBs if they are not labeled. If you can get the schematics so much the better, but label each CB when you find out what circuit it protects.
If all the CBs have 120 volt output, go to the dead outlet closest to the panel and open that up and check for power, and check each one until you have checked them all. It is a hunt and find situation without a schematic, it can be hunt and find even with the schematic.
As noted there is often a second GFCI or even a third, typical locations are bath, kitchen, outside utility cabinet, all of the weathertite boxes on the side of the rig. Cabinet mounted may face out so you can see them, down which is often missed, inside the cabinet, inside any exterior cabinet, especially one with plumbing exposed. I think they like to hide them from us. When labing your CB panel, note any circuit with a GFCI. The panel manufacturers often include labels for that when you purchase a new panel.
For the initial search, a non-contact tester is adequate, is fully insulated and it only has one probe, therefor, it only requires one hand to use.
Okay, here is a blatant ad, a "brother P-Touch label maker" is a great bet for labels in a RV. Weather proof and very clear, color tape and print available, and very professional looking. I'm not in any way connected with the "brother" products, it's not blatant in that way, it's just manufacturer specific.
"I travel not to go anywhere, but to go. I travel for travel's sake. The great affair is to go". R. L. Stevenson
David Bishop
2002 Winnebago Adventurer 32V
2009 GMC Canyon
Roadmaster 5000
BrakeBuddy Classic II
