Hi VW77,
This sounds like to me that the latch itself is either broken or frozen. So when you turn the key or use the release the rods (#9 and #4 in the attached diagram) that are connected to the lever (#5) on the latch, do not actually release the latch.
If it is frozen, then the key will feel very hard to turn. Pressing down on the liftgate over top of the latch to relieve some pressure may allow the latch to release. Once it is off, you need to either replace it or lubricate it with a spray lubricant so that it loosens. You can operate it with the key while spraying it and it should loosen up.
If the latch is broken the key will feel very easy to turn, in this case there is no easy way to open it. You may have to remove the interior panels to gain access to the latch to release it manually. This is not easy with the lift-gate closed. I am not suggesting this but some people end up cutting a hole in their panel in order to gain access and then replace the panel. I have never had to do that, but have seen it done.
Let me know how the lock cylinder feels when turning it and hopefully it is just frozen and the trick above works. If it does not, we can come up with something else.
Thanks
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Wednesday, April 17th, 2019 AT 5:50 PM