Key fob

Do you have a second fob? If yes try it. It could be a low battery in the bad fob or bad switches in it. But without a second working fob you cannot just change the battery or take it apart. You need a dealer to reset the system for the single fob to work.

It sounds like you have an alarm module going out but to be sure I would double check all of the system fuses becasue that is more than one.

Here is a wiring diagram to help you see what fuses need to be checked.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Please let us know what you find.

Cheers, Ken

If I remember correctly the BMW alarm module is a dealer installed unit. Plug and play as the wiring is already there. A 3 button remote with lock/unlock, panic and alarm arm/disarm on it.
Do you hear 3 chirps when you try to lock/unlock the car?
If so it is likely to be a bad actuator sense switch, there are switches in the door locks as well as the hood and trunk. They tell the BCM and alarm system if the doors/hood/trunk are closed. If any of them fail the locks will not respond.
The problem is determining which switch is the problem. Normally the doors and trunk will show a "door ajar" warning. If you don't see that it is probably the hood switch. They are a common issue. The test is to disconnect it, if the door locks start working you found the problem.
You can also look at the switch status on a factory scan tool. It would tell you which one is bad real quick.

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