First of all, you should check if there is a blown a fuse in your 12-VDC fuse panel, because the slide operates on your coach battery.
If the fuse for the slide isn't blown and there is voltage out of the fuse box, pin for the slide, then check if there is voltage on the slide motor when you operate the switch for the slide but the motor doesn't turn or click then your slide motor has a problem.
I would suspect the fuse in the fuse panel as your culprit or your coach battery voltage. When is the last time you checked the water in your coach batteries, how old are your coach batteries, and what is the voltage reading across your coach battery terminals? Hopefully one of these things is your real problem.