How can I fix locking issues with my Golf Mk4?

I am having problems with locking my golf, when I click the key control it doesn't do anything but the battery is fine as the red light comes on when pressed.
I can lock all 4 doors by using the lock on the drivers door but no matter what I do the boot will not lock?
I have changed some bulbs in the rear lights and had this problem ever since.
Help and advice would be much appreciated.