Long Islander

I removed the tailgate interior lamp housing -- this is the one that is on the inside of the tailgate which illuminates downward when the tailgate is open -- so that I could replace the bulb with an LED bulb. When I reinstalled the lamp with the LED, it didn't light up, so I assumed the LED was faulty. I reinstalled the OEM bulb, but that no longer worked either. I tested both the OEM bulb and the LED in other locations and they both work fine. I also tested the contacts on the tailgate lamp housing with a tester and I get no voltage.

Any clues? I hate to have to go to the dealer for such a minor issue.