Hmm. This thread reminds me that my light has been out for months but I haven't replaced it. All i can suggest is popping off the plastic trim on the inside back of the trunk lid and follow the wires on both lights. If you can't find a split in any of them, check the security of the ground. If it still won't work, either splice the wires or let it be.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>