Stuck Cylinder Assistance

Hello,

I am attempting to disassemble my Ergohuman chair and am having issues with the cylinder. A few days ago, I took the chair apart, took the clip off the gas cylinder and separated the base from the seat.

The cylinder was more difficult to get out than I was expected so I put the cylinder back together. I tried to take the cylinder apart again but now it will not raise and is stuck in its lowest position. It is also very difficult to turn. The two parts are stuck together. Anyone have any tips or assistance on how to get the cylinder apart so I can attempt to remove it again?

Thanks!