There are about a half-dozen ways for this to fail.  Do you hear any motor sound?  there could be an object lodged in the mechanism. I once had the parking break sensor break.  Good luck. People might need more info.

Stephen & Susan Mills wrote:

Not sure if this will help as you didn't mention which mechanism you have.  The attached is for the Power Gear Slideouts and will give you a number of options to get your slide in. Hope this helps.