Looking for a little help with a tail light problem.

I have a 97 F-150 and just got a repair order for no tail lights. The brake lights, blinkers and flashers work, but no tail lights or license plate light.

Fuses is ok and the bulbs are new. I checked the wiring for obvious signs of a break or loose wire, but didn't see anything.

Any ideas on what the problem may be or where to begin looking?