There are two methods of syncing diamond keys if 1st method fails try 2nd method, just had to resync my keys after the unlock button failed, put a new board in the key and used method 2 to sync mine.
Programming Additional BMW Key Fobs
So if you have a working key fob, but wish to program additional keys, follow these steps:
Take the working key fob along with the ones you want to program inside the car with all doors and windows closed.
Put the working key into the ignition and turn to position 1. At this point, the dash lights and accessories should turn on.
Turn the key back and remove.
On the working key, hold down the unlock button and press the lock button (the BMW logo) 3 times, then release the unlock button. The doors will then automatically lock and unlock.
Take the new key and hold down the unlock button while pressing the BMW logo 3 times, then release the unlock button. Again the doors should lock and unlock, and you’re done.
Programming a New Key from Scratch
These instructions are for programming a new key when you do not have a working key fob.
Insert the key into the ignition and turn it to position 1 and back rapidly 5 times.
Remove the key
Hold the unlock button and press the BMW logo 3 times, then release the unlock button.
If you have additional keys you’d like to program at this time, repeat step 3 within 30 seconds from the original key programming.
Turn on the ignition to complete the process.