Trailer brake controller

Alright all Tundra guru's. Bought new bumper pull trailer on Friday, salesman brought his tester and plugged into the 7 way plug in the bumper. All lights except the brake lights tested good. We figured out how to turn brake controller on, still no indication that the brakes were working. Got trailer home and this morning connected up the trailer, the green indicator on DIC was lit. Went to the setting that indicates gain and unable to get anything showing that the TBC was working. Dealer said that they would be happy to look at it Monday. Explained to Service Manager that business hour days were hard to get off.
Couple of questions for y'all. Which fuses under hood would control the TBC? Is there a fuse in the drivers kick panel?
Just for clarification the trailer lights are incandescent. Tail lights on truck have been converted to LED with resistors, lights on trailer except brake work. I know if and when I get the truck and trailer to dealer that their response is that the "truck checked out fine". Really frustrated.
Thanks for burning brain cells on this Turtle

 

bump

 

I’d try swapping your taillights back to OEM bulbs and see if that fixes it. Seen plenty of problems due to LED’s back there. Other than that, the factory TBC on tundras are known to suck...

 

Pulled trailer with truck to dealership on 10/25 to get checked out. Dealers response was "truck checks out fine." Discovered that brake lights were indeed working on 30 plus mile ride to dealer. Tried to get gain to work at red light just before dealer and it showed increases in gain. I guess that the paint had to rub off on new trailer coupler to ground. Trailer brakes have worked great since. Sufficient ground proved to be key. Thanks to all that have given this some brain time. Will be back later IF problems with Tundra arise. Turtle