Sudden no crank no start issue

That could be caused by a few items. One would be a bad key, do you have another to try?
There are a couple fuses you can check, Fuse F14 and F67 both power the EWS.
Next would be a failure in the key detection parts, the ring antenna or the EWS control module. Testing those requires a dealer level scan tool that can read the security system data and allow testing of the system. Unfortunately BMW has made their system so that it is very difficult for anyone to work on the security system, The EWS requires programming through a dealer to get it to work and you cannot install a used part, the EWS has to be new.