I seem to have the same problem with a European 2000-2005 Focus. My rear door would not lock and the lock button on the door would not press in to lock. The central lock would not work either.
Any new advice on that? I couldn't find anything better than this thread.
I managed to take apart the door's panel & insulation and then to unscrew the lock itself, but I didn't manage taking the lock mechanism out as it's attached to the outside handle and it's too difficult seeing what's inside the door's body.
I'm afraid a mechanic would just replace the whole assembly for too much $$$.
It can't be something requiring a reset, can it?
Any advice on how to take the lock out or otherwise fix this? Maybe schemes of how things look inside the door?
Thanks in advance for any idea!