That's one of the common leaks, I think it might be called the 'wet seat belt' leak, but I think there's actually two potential leak spots along the roof gutter, and maybe only the front spot is the 'wet seatbelt' one.
In any event, the easier one to access - and the one that's probably causing your leak - is under the little plastic trim piece on the roof gutter. It's at the junction where the roof gutter meets the rear hatch upper corner. There's a seam under that trim that's glued or caulked in some manner, and the material gets brittle and cracks when it ages.
When I had a small leak in that area, all I did, as I recall, was remove that trim piece and clean out the area - the water that hits the roof and flows into the 'gutter' can then easily flow past that junction and down the hatch gutter. Otherwise the water pools and then flows into the cracked seam/s.
The other potential crack area is above the door and you have to remove the plastic moulding-thing above the door to access, which can be a pain.
Beyond cleaning, and probably what you should do, is fill any cracks with a black silicone sealant, like a 'window weld' or maybe a gasket sealer. Avoid the generic hardware store-type clear silicone, as that stuff will get moldy over time. Someone else may have a more specific recommendation of what product to use.
I did find some cracks on the hatch hinges, the PO (curse that person for so many reasons) installed some type of superpowered shocks and the force from me trying to push the hatch down has shown up on the hinges.
The only thing that comes to mind is called 3M window weld. I just looked it up on Amazon and it's a urethane-based sealant. So maybe a urethane-based sealant would be good, rather than silicone. If you find a small tube on Amazon of the 3M stuff, or wherever, then fine. I'm only seeing big expensive tubes. I'd think you'd be able to go to most auto parts stores and find a small tube of a urethane-based sealant that'd work...
These are just my guesses though, in case no one else comes up with anything they're probably better than nothing. Truthfully, any decent sealant would probably do the job just fine, even though I said avoid clear silicone. I mean, I've used clear silicone myself for such things - and it works.