My $/£/€ 0.02: in 2023 bought a new fob/remote from BMW as the one I got with this rig was long dead. Remote lock/unlock worked fine until one day it just stopped working. I thought maybe the battery in the remote was dead already despite being new (new old stock, maybe sat on a shelf for 20 years?). Went to a battery/key shop and it passed transmit tests with a strong signal.

Did the re-pair procedure: key in ignition, turn to position 1, turn back, remove key, press the buttons in the right order. Nope. And another nope. Had to do that three times before it worked again. This happened last month too, when my fuel pump died, and again it took 3/4/5 tries at pairing before it worked. So maybe keep trying? My central locking system worked fine from the door lock and the console switch, sounds similar to your issue.

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