I had the same problem with my 2018 Silverado. I hooked up my trailer lights to my wife’s car and they worked fine, when I plug them into my truck they wouldn’t work and even blew three fuses under the hood. I finally figured out that a ground wire needs to be connected to the each light fixture at the back of the trailer. I just spliced into the white wire at the plug and then ran two wires down both sides of the trailer, then connected to the nuts that hold the lights onto the trailer.
Once I did that, they worked! Hope this helps!
