West8 - Keep me posted with what you find. I have the same issue currently with my 2024 GMC Denali 2500 with a new 2023 Rockwood Minilite trailer. On my first trip, I got the "Check Trailer Wiring" on the DIC. The camper dealership attributed it to a connection issue with the 7-way connectors and the truck. After "pushing" the pins together in the 7-way, it seemed to fix the problem for about two weeks, then the message returned. The camper dealership used dielectric grease in the 7-way, same issue. Replaced the 7-way connector on the trailer and did some basic testing of the braking system (by measuring the amps to the brakes when the emergency pin was pulled out) - the same problem. We then replaced the 7-way receptacle/plug on the truck and the same issue returned.
For better or worse, I decided to head to the campground with the DIC message occurring constantly. After about 45 minutes of driving, the DIC message stopped and hasn't happened again (the drive back was about 2.5 hours). I have an appointment at the GMC dealership to see if they can diagnose anything on the truck.
Side note: The lights worked all the time. On the dash, I put the trailer gain setting up, which made it easier to tell if the brakes were working or not.