The first thing to do would be to drop the non working light closest to the fuse box and check for power and ground . Most RV's are wired in the quickest / cheapest way possible , that involves a single wire from the fuse to the furthest load in the circuit, and connecting the other loads along the way with " quick locks or scotch locks " . These devices are quick to install but can be troublesome over time , because they cut through the wiring insulation and some of the strands inside , weakening the main wire that can break over time.
If you have no power to the wiring then you may have a hidden or unmarked switch.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.