no power at trailer hitch

How are you checking it?

Not all trailer hookups are wired the same nor are the trucks as per age and model. Either find a wiring diagram or Turn on driving lights, and hit brake pedal and turn on blinkers and while doing so use a multi-meter or test light ground to frame or battery to see which wire is which, ground should be easy to find, may need to ground it to your trailer ground too with a jumper while testing/locating trailer wire configuration, figure out which wire is which on the trailer and match them together, you can use a plug adaptor or cut your trailer wires and splice them in correct position for your truck. But if you do not have power to trailer plug find your ground wire to frame and check it for good contact, Follow the plug wires to find the ground coming out of harness and check all wires separately with multi-meter. alligator leads, while in ohms.