uPVC Conservatory Door - Won't Unlock?

I have recently bought a new house and changed the lock on the conservatory door.
the lock matched and was working when testing locking / unlocking. After locking up after a day of painting I came back to try and unlock it.

The bottom half doesnt seem to unlock?
The lock turns and seems to lock / unlock.

But only the top half seems to unlock?

Is there a way to get this unlocked without ruining the door itself?