Hi jshelley,
Welcome to the Heartland Owners Forum. Sorry you're having a problem, but it may be simple to fix. The slides are powered by the battery and run off 12V DC. The battery gets charged by the Power Converter which changes 110V AC into 12V DC to charge the battery and provide power to the 12V fuse box.
There's a manual-reset mini-breaker in-between the Power Converter and the battery. If the breaker trips, the battery doesn't get recharged and will run down. The large slides are operated by a hydraulic pump that takes a lot of 12V power. If the battery is discharged, you typically won't be able to operate the slides.
The mini-braker is in a row of breakers located near the battery. The reset button is on the breaker that has two large diameter red wires attached, but the reset button is teeny tiny and hard to see. I've attached a picture.
We also have an owner written 12V Block Diagram and Diagnostic Guide that explains all this more fully and includes diagrams, photos, and a diagnostic flow chart that may help if it's not a problem with the breaker having tripped.
Here's a link.