New guy here with a tail light problem.

[Mike P]

I just recently purchased my first Porsche, an '80 SC and am having some R side tail/brake light issues. The R rear side running light works, turn signal work, reverse light works but the brake/tail light doesn't. Ive replaced the bulb, checked the fuse, disassembled and cleaned the contacts, still nothing. While I had the tail light assembly apart I tested everything and it all worked, put it back together and back to no R tail/brake light. Unfortunately I'm at work and don't have a volt meter with me so I can't check anything that way. Does anyone have suggestions, is the bulb holder in the housing faulty, is the housing not grounding appropriately, etc...? I'm kind of at a loss. Thanks in advance for any help or suggestions.