2001 bmw remote keys stopped working

Both key fobs? Did you replace your battery recently? https://forum.bmw5.co.uk/topic/135358-key-fob-remote-sync/

VRoom12345 and Bob_, thank you for your replies. My initial question did not include important info, so here is a better description: My 2001 BMW 530i was in for a service that required the 12v battery to be disconnected. After this service, both remote keys failed to lock or unlock the doors. Background info - the battery in the remote key is charged when the key is in the ignition switch while in the "on" or "run" position, and the remote's battery cannot be replaced, so if the battery fails, a new key has to be obtained, cut to fit the ignition switch, and then re-programmed. Both remote keys are original (21 years old), so it seems plausible the battery in each remote key will no longer hold a charge, or perhaps the charging function provided by the ignition switch is not working. But there may be another reason. A standard security operation of the vehicle not directly related to the remote key is the doors automatically locking when the vehicle reaches 4 mph, and this operation does not happen any more and stopped working at the same time the remote keys failed to operate the door locks. So while the path forward might be (suggested by local BMW service) to have two new keys made, cut, and programmed, which is very expensive, I wonder if the problem is with: 1) the ignition switch charging, or 2) if some computer tied into the security system has failed as indicated by the automatic door locking operation not working. Any thoughts? Thanks again in advance for any advice.