Originally Posted by Wallowa
As my old memory serves me the technique that might work is to plug in the spare "new" antenna, invert it over the old antenna-key way and then put your key in and try it..
I also understand that once you start it the antenna is NA...and can be unplugged and stowed..
Give it a shot...good luck!
The dealer also suggest getting the new ring as far away from the old ring as possible/interaction. I don't think this is a BMW workaround, but trying all of the permutations/combos that one could think of. E.g. disconnect the battery, which implies a truly 'cold boot'. But if any of them worked once, I'm not convinced it was not coincidence and not a slam-dunk cure! Sorry to bring bad news...am seriously thinking of getting another pig barge as it's the only tourer in the inventory without CAN-bus.