I have power to my camper, and outside lights when hooked up to the truck. I have one rear light that will go on when I hit the blinkers or hazards. I have no running lights breaks or signal lights. I have test and have no continuity form the tail lights. I cleaned the ground wire on the camper and clean the replaced the portion of the 7 pin on my truck. Need some help.
Almost always when I come across a problem like your are having I find the ground is bad somewhere.
On my bumper pull trailers it turns out to be not grounded between the hitch and the ball. Often a drive around the block will fix it.
Check continuity between the frame of your trailer and the frame of your tow vehicle. Last time I had this problem I ran a ground wire between the frame of the trailer and the truck. My lights starting working so I hunted down fault.
2013 Voltage 3905
2013 F350 4x4 DRW
2013 RZR XP 900