Had this problem with mine too! If the fuel flap is also not working it could be fuse 14, found on the rhs of the driver's seat. If this is ok then it's most likey to be a faulty driver's door locking module. The bad news is that it is practically impossible to gain access to the tailgate locking mechanism unless it can be unlocked. Try operating the locks a few times, with the remote, while standing by the tailgate and trying it at each unlock. With luck it may open. When it does I suggest you remove the tailgate inside cover and cut a small hole (2" x 2") to expose the lock. This will, at least, allow you to flip the lock open from inside until you replace the driver's door module. A new module is about £150 and takes about 2hr and a lot of patience to fit!
