You can try squirting some lithium spray grease up into the slider area (under the rubber accordion fold cover). It’s possible that the shaft is bent, and if that’s the case it will be difficult to fix.
You can also try taking conventional grease and working it into the slider area with your finger, but if the suspension isn’t moving at all you won’t be able to get the grease to go very far upward. -Paul from ESG
