i90689

I just had my 2018 Equinox Premier set up to be towed. I had a Blue Ox base plate installed, and they used the diode kits for the lighting. When I tested the lighting the tail lights and left and right turn signals were fine, but the brake lights are not working. I checked all the wiring from the coach through the pigtail to the front socket on the car and everything looks fine. Anyone have any ideas before I drive the 63 miles back to the dealership??