Don't know where you had your wiring harness installed but if it was UHaul
they probably screwed it up. Every time I've had them install something they pork it. First they installed a hitch, when I got home I looked underneath and only 3 of the 4 bolts were in. Took it back and they said they had a hard time getting the bolt to line up so they skipped it. WTH!?!? Then when I was rewiring my trailer I had them install a harness. Got home hooked up my tv to trailer and nothing worked right. Double, triple and quadruple checked my work....researched trailer wiring schematics on line. Nearly went crazy tring to find the problem. Lo and behold the "professionals" at UHaul
wired it incorrectly. Once they fixed it I got home hooked up and everything worked.