'98 SLK230, sat for 2 years.

The vario top is completely non functional. There is no fluid in the hydraulic pump. I see evidence of hydraulic leakage on the rigid piece under the headliner. The headliner fabic has come detached and I can see stains in various spots around the periphery, so I assume the hydraulic ram up there has a bad o-ring.

So- I'm trying to get the top to unlatch so I can work on it. It appears that I should turn a 6mm hex key clockwise to unlatch. When I do so, I feel something stretching/bending, but it never unlatches. I'm able to turn about 30 degrees or so, but it springs right back.
I wonder if there is some other trick to this to get it unlatched?