For the slide to work you need a fully charged battery, good fuse between the slide switch and the battery and the slid room must not be hanging up on anything. I'd crank the slide out manually first to check to see it's not catching on anything and WILL move freely. If it cranks out easily, then check the fust (it wires directly to the battery and the fuse should be located in the positive line fairly close to the battery) and finally make sure your battery is correctly charged. IF you find it binding when cranking it by hand you'll need to find out where and why and correct that problem.
Good luck / Skip