Sounds like you have an Open somewhere in the circuit.
First test for voltage at the female connector on the TV. If you have voltage there connect the umbilical cord and test for voltage at the trailer end of the umbilical cord, where it enters the trailer. If no voltage there the open is in the cord. If voltage there the line going back to the brakes is likely open.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles