Try locking from the passenger door lock next, or the trunk. Central locking works okay doesn't it?

Fuses are good to check, it is also possible that the security module was not operating properly and is disconnected: Black box marked: Becker under the passenger carpet & plastic floor.

Do you have the (optional) keyless entry? That could also be a "key" piece of information ;~)

__________________

Gone to the dark side

- Jeff