I would start with a mutimeter and check the switch, then the slide motor. Or visa versa, whichever is easier. Unlikely a fuse if the other slide works.
Can you lift the sections from the cargo tray to access the motor? Have you tried the switch on the other side?
Bob in College Station, TX
2015 Entegra Cornerstone 45K
2012 Jeep Rubicon, 1994 FXLR