Since you didn't do the initial install, why don't you take it back to the dealership who did the install?
I'd be terrified to take anything electrical to a dealership but since you did, why not hold them responsible? I once had a short in a brake wire and was appalled by dealer tech's repair which consisted of twisting new tire with no crimps, solder, or even wire nuts and simply wrapping it up in electrical tape. I now do all work on my of my vehicles to include trailers by myself. Too risky to trust someone else to do it.
If you are going to trace it yourself check following:
-- inline auto-reset fuse that all brake controllers should have installed
-- Connection from brake controller to brake pedal switch
-- Did you manually apply the brake controller? If so, did anything happen?
-- Check voltage at trailer plug
-- Check all wiring, don't assume it was hooked up correctly. Does your controller have power to it? Did your truck come with factory installed brake controller wiring and all it needed was a specific connector to your controller? Please provide more specifics, thanks.
Good luck and hope you find it.