Richard,
Using a test light on the motor home plug, the 3:00 o'clock pin is the right turn signal and brake light signal and the 9:00 pin is the left turn signal and brake light signal. Have someone step on the brake pedal in the coach and see if either pin light up your test light. If so, then the issue is in the male plug. If there is no light, then the issue is on the coach side. Either in the plug, no converter, no power to the plug (fuse).