Dragonfly X2 / Stingray X2 - Part No. 03 - Cap

This is the old style Cap and not suited for X2 models.

If nothing happens when the Cap is turned and it won't go softer or harder it's probably the Adjustment Screw that is damaged and not the Cap.
First make sure that you feel under the Needle Bar Pin and not over when feeling the adjustment.
If you can't change the softness by turning the Cap it's probably the hexagon on the Adjustment Screw that is damaged.
This can happen when it is tightened to hard in the bottom. If this is the case you need to purchase a new Adjustment Screw.