Hmm hadn't thought of the alarm system.
If I had to guess I would say it's disconnected but I should take a look. The central locking system is not working right now either. *sigh
The trunk is not locked thankfully. I can open and close it with the outside button fine, but not lock it with the key. I should have specified.

I just took a peek and don't see any wiring going into the lock mechanism....
Only the vacuum/pressure actuator which is disconnected.

Cheers