Have you found fused for overhead lights. I and others have hidden fuse locations after year/s of ownership.
You really need to test for voltage. Ballast can be bad use known working both bulbs or swap ones in there to test them. One bad will keep both from working.
Two shared light "3way" switches have extra pole on each could fail. Butt connectors above lamp base from rough in electric could be messed up. Also grounds can be a daisy chain. I have dropped out another lamp when poor grounding with 3wires in single butt connector was disturbed/pulled out , when I was working on FF fan vent.
95 Monaco Crown Royale
M11 400hp, 4060 trans.
Aquahot, Generac Guardian7.5k