I recently installed aftermarket Taillights. Since the install the reverse light on the passenger side has not been working. It does work if I remove the taillight and just let it hang, but one I reassemble and tighten the taillight back in it stops working. There is no issue with the drivers side.

 

Are they using the regular bulbs, or are these replacement lights as well ?

If they are using the factory bulb, and connector, it might be on of the wires got pinched, and has broken the wire.

You will need to carefully inspect the wire for breaks in the wire, but maybe not the insulation.

If they are similar to LED tail lamps, it could be a defective tail lamp ??