Where is the new wiring ( TV or trailer)? Check wiring on trailer, FR uses wire nuts to connect the brake wiring. These can disconnect and short or open circuit. If you have an ohm meter, check the resistance between the brake pin on the trailer connector and ground. It should be low, but not zero. For single axle trailer resistance should be 2-3 ohms
for double axle trailer resistance should be 1-2 ohms
Check bargman connector for dirty or damages pins.
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