Welcome! Some more info would be helpful. Since 120V AC outlets are working, I assume this means you are plugged in to shore power.
Regarding "dome lights" not working. Do you mean the lighting throughout the interior of the camper? These operate off of 12V power. Here are some questions/ideas to help troubleshoot.
Does the camper have a battery installed? If so, do other 12V items work such as water pump or refrigerator on the gas setting? If no other 12V items work, that means the battery is not connected in some way. Could be a faulty battery, loose connections, or blown fuses.
If there is a battery installed, is there a battery disconnect switch that might be engaged (set on disconnect)?
There is a resettable inline fuse that should be near the battery terminal on the positive lead that could be worth exploring.
There is also the power distribution center inside the camper and the fuse for the lighting circuit may be out.
Also reverse polarity fuses on the converter that may be blown if the battery was ever hooked up with reverse polarity.
Some excellent reading material.
The 12 volt side of life