Seat won't go up and down

[2003S]

I had a similar situation. With with the manual seat, the height lever attaches to a cable that activates a hydraulic cyclinder. In mine, that cable had gotten mangled some how. I could activate it by pulling on the cylinder's attachment point directly with a vise grip, and adjusting the seat height. I left it that way, since I'm the only driver, don't have much need to change height regularly...

If you move it all the way back and get under there with a flashlight, you should be able to see all the moving parts...

If its a power seat, I have no idea.