1988 Chevy Truck tail lights don't work

I recently reran an antenna cable through my dash. Afterwords my tail lights quit. I've checked them with a tester & I have power all the way to the bulbs(which are good), but no lights. I'm thinking there is a ground problem. Is there a ground wire for the rear tail lights under the dash? My license plate lights work. I have a shell with a 3rd brake light spliced into the drivers side tail light harness, both the ground wire & hot wire light the tester, it has to be a ground problem, but where? I have to have disturbed it under the dash somewhere, any clues as to where it could be? Thanks in advance