Passenger headlight inop but bulb and DC power present

:h
Hmmm....
Doesn't sound logical does it? What you have done for testing it is all good. Theoretically it should work. Especially if you have 12V and provided an alternate ground.

Does this system have the provision that many newer vehicles have for shutting off a headlight when you turn the signal light on?
If so, I wonder if its possible that has anything to do with it. Perhaps a malfunction in there....