I know it sounds basic but start at your truck wiring and work backwards. you need to make sure that your 4-way on the truck is working as it should, if you haven't already done so. If running lights, turn signals, brakes all work, then move on to the trailer. I have seen many vehicles with separate fuses for trailer wiring. if it's your 60, that's likely not the case but I know that my Silverado has separate trailer fuses that gave me an issue once. The tag light had a bare spot and kept blowing the fuse for some reason.
Good Luck. Trailers are notorious for wiring issues.