Just keep in mind any of the DOT SAFETY LIGHTS all get their power from the Truck side. These have no connections to your trailer 12VDC distribution panel...
I would look around where the underbelly maintenance was being performed and perhaps some wiring got severed or unplugged...
If they had to drop the underbelly covering which is alot of work I would let them do that haha...
Sounds like all of those lights you mentioned are DOT SAFETY lights... Might use caution when pulling the trailer down public highways until they all get fixed etc... Nothing worse then being pulled over for equipment issues...
Roy Ken