I know this comment is a bit late, but I ran into the same problem and I found a solution that at least worked for me and would like to share in case someone new finds this forum with the same issue. If you are worried about denting the rear hatch I don't recommend trying this, but if you are driving a 10 year old or older Subaru, you likely have some dents anyway from everyday use and one more wouldn't matter. I have a 1999 Legacy wagon that I took ownership of a few years ago. The lift gate had worked flawlessly since I owned it until recently while moving to a new house. Really bad timing.
My solution is rather simple and based on an assumption that it didn't close correctly jaming the latch in the wrong position or only was only partially locked. I gave it a firm kick (with the flat of my foot not just the heal) just below the license plate at the bottom of the door. That did it! It came unstuck and has been working fine since! Fortunately this didn't result in a new dent for me. The bottom of the panel is fairly well reinforced and you are only pushing against the stronger door frame anyway. This is much easier than crawling in from the back seat and attempting to pry the panel cover off.
