Hi - I am also unable to reprogramme the display by holding the BC button down and my issue is when I attempt to start the car I get CODE---- displaying on the computer strip on the dash.
A mechanic with BMW software could not get the software to 'connect' to my cars system so no full diagnosis, with a 'LAUNCH brand' tablet scanner he was able to -re-initialise the imobiliser system but that changed nothing. turning the key does nothing (no click, no starter engaging just silence)
New battery installed now and still the same.
Does any of these issues sound familiar to you chaps
The car handbook tells me to utilise the MID unit on the centre console to input a code. neither my car nor a friends ever had a MID unit (different dash configuration)

current vehicle is:
2004 X5 E53 sport diesel 3.0L