Vectra JSII 2000: Driver door lock stuck?

I remote locked my car and went to pay for my petrol. When I returned, remote unlock and manual key unlock does not open my driver side door. The 3 other passenger doors continue working ie. unlock and lock using both remote and manual key.

The remote lock however, no longer clicks twice to deadlock. The key does not register the second press. i.e. 1st press - standard lock. 2nd consecutive press - deadlock.

It is a real pain having to get into the car from the front passenger door.

How can I fix this problem? Thanks!