Tail lights, not working at all

[cranky84]

69 gmc c10, none of my light in the rear are work. No parking, blinkers, brakes or reverse lights are working. They worked not too long ago... I disconnect the plug in the rear and in the firewall. Bulbs are good. I used a tester to test the fuse and it works but after all of this it doesn't work anymore? With a test light I tested the wire. Brown, dark and light green, and yellow, brown is the only wire that has power, I am checking at the firewall. As far as grounds go, is there two separate grounds one for each side? Do I need a ground to the bed to the frame? I'm lost with this