pop off the truck lid carpet and check the wireing from the light as far as you can. Somewhere you probly lost a ground or a terminal sliped off or something you you might have cut it somewhere working on something, maybe. just check teh ground for that and the power terminal. If al else fails, just run a new circuit using the running tailight power and make a ground or something like that.
Good luck hope you can figure it out.


Roca