I have a 2007 Fisher Nirvana hybrid, came equipped with an RST Vogue suspension fork.
This fork has the pushbutton type lockout.

For some years this has been my foul weather commuter and I left the lockout in the "rigid front fork" mode. Now it won't go back.

I do not think it is the actual shocks themselves that are jammed. If I unscrew the cap on the side that has the lockout button, the suspension travels normally. Also, the pushbutton remains in the "down" position even after you push it (originally it would reset to a higher position when not in lockout mode).

I contacted RST. They don't offer replacement parts for this fork.

There is a screw in the middle of the pushbutton. I unscrewed that and removed the metal cap that forms the button. Sprayed some penetrating lubricant in. No go.

Any further suggestions?

I would like a bit more off-road capable bike, so my cheap immediate idea was to put some more MTB-ey tires on it, free up the fork, and call it an almost-mountain bike. Before I'd do anything major like replace the fork, I would probably just get a used MTB.

But if I can find a way to get this suspension working again, I'd take it.