So the slides are probably driven by separate electric motors. If the non-functional slide doesn't move or make ANY noise at all when you press the switch, it's probably an electrical problem. The 12V DC to operate the slides probably comes from the mini-circuit breakers near the battery, but possibly could be powered through the fuse box. So first thing to do is check the fuse box to see if you have fuses labeled for the slides and if one is blown.
If that all looks good, carefully remove the switch from the wall and immediately take a clear picture of the back side so if wires come off during your investigation, you'll know how to put them back. Check the voltage at the switch with the switch at rest. Find a good ground for the ground lead of your voltmeter. If necessary, you can usually find a ground behind the cover plate for the fuse box. If you have 12V at the switch, press the switch and check other contacts to see if 12V is getting through the switch.
If all of that is ok, OR if you do hear some noise when you press the switch, you'll have to locate the motor for that slide and check the electrical connections and/or the mechanical chain/cable connections.
Perhaps someone else with a Torque and comment on where the motor is located. If no one knows and you can't find it, on Monday, call Heartland Customer Service at 877-262-8032 / 574-262-8030. Have your VIN # ready. They can get that info for you.