Hi dpuhlein,
Welcome to the Heartland Owners Forum.
First thing I'd do is call Heartland Customer Service at 877-262-8032 / 574-262-8030. Have your VIN # ready. Even though you're a little out of warranty, it's possible Heartland may help. It won't cost anything to ask.
In terms of troubleshooting, is your battery charged? Are other 12V systems working when not plugged in to shore power? Interior lights, furnance, refrigerator?
There's a row of 12V mini-circuit-breakers near the battery, one of which is usually a manual reset. If it trips, the battery won't charge while on shore power, and can run down too low to operate things like landing jacks. I've attached pictures. The reset button is teeny-tiny and hard to see.
Also, on the electric front jacks, I think there may be an inline fuse in the wiring bundle. Others may have more detailed guidance on this.