Help, 2018 2500 ram trailer tail lights

I have a 2018 ram 2500, Cummins, 600 miles from home. taillights?&src=tdr">tail lights on the truck work, tail light port on the trailer plug is dead there fore the trailer tail lights don’t work. I have trailer brake and brake lights , left and right turn and hazards. I have checked the fuses in the main box at front left battery, everything is good. Even went through the fuse panel with a test light and everything checks out. Called my dealer back home and he said the Ecm sensed high voltage and shut the circuit down and will need to be plugged into with computer. I don’t know that I believe him, but local dealer said it would be Tuesday before they could get me in, and I ain’t waiting that long.

I had a similar issue on my ‘15 3500, and I remember finding a blown fuse that didn’t say it was even related to the taillights on the trailer, but it fixed the problem. Think I even wrote it In The manual...bit doesn’t do much good now that I traded!

Can anyone help me out? I know it’s something dumb. Going to unhook the batteries and see if it “resets” whatever breaker might be blown.

Thanks