If you are referring to the inside camper lights, many are connected is a daisy chain hook up. Meaning they run 2 wires from light to light in a chain type fashion. They are still wired in parallel however if the very first one in the circuit becomes loose in the wiring, it can prevent all the down stream ones from working.
You can try and take down a fixture that is not working. The wire is stuffed up in the ceiling or in the wall depending on the fixture. They used wire nuts most times and one of the connections may have come apart or loose.
I would start with the one closest to the power converter and take the fixture down. Odds are high the wiring to the closest one is the one first in the line. If you have a volt meter, check the power at the fuses first, then work your way to the lights fixtures. If power exists at the fuses, then you have to track down where the wire is unhooked. It may also be a ground wire that is unhooked and not the power wire. If 12 volts is at all fuses, then use the meter at the first fixture and use a ground from a different source. It may be the hot wire is all intact and just the ground is loose or not connected.
Hope this helps
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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