Tailgate will not open
 

I have an Outlander 2008 European model and yesterday, the tailgate decided that it would not open.

The handle makes the usual noise but it will not un-latch the lock.

For background info, I had locked the doors with the central locking switch on the door panel and then unlocked them when I stopped the car. All the other doors unlocked as normal, but the tailgate did not.

I have tried many times to open it after switching the central locking on and off, both using the switch and the key-fob but with no joy.

I have also tried to open the tailgate from inside through the little access hole without success - it is solid.

Has anyone else had this problem? Does anyone have any ideas how to sort it? Any help would be appreciated, thanks.