rear light installation?
Hi dory. That's really difficult to answer without laying eyes on the problem. I assume you know for a fact that you have the correct assembly to install. You should consult the Chilton's for your car if you haven't already. Or if you are brave you can start to disassemble the other tail light to see if you can see the hurdles or whatever is blocking your way. Don't let frustration vapor lock you either. Walk away for a while and/or get some fresh eyes on the problem. Good luck!
Search BMW 5 Series Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
BMW 5 Series Experts