I've just noticed that my tailgate lock doesn't lock using either the key or remote. All this time I've just thought it was locked when using the remote as it gives the nomal clicking sound both during lock and unlock. All the time it's been unlocked!
My memory is that when locked the button just goes in and out without engaging anything.
Any tips?
Correct!, button simply pushes in with out any resistance when locked. Take the inner cover off and have a look at the actuation rod. Sounds as if something has simply come adrift.
i'm going to take a guess and say that you have broken wiring in the tailgate harness that goes from tailgate to body.
If there is a clicking sound when the lock is actuated, the power cable must be OK!