You don't mention what year HC you have but if it has the old style standard electric jacks there are lots of options. If you have the Level Up electric jacks then I can't help.
The old style jacks have replacement parts available as well as complete replacements. You will need to remove the leg (see below) to diagnose the problem. It could be a shear pin (easy fix) to stripped gears or shaft (a little more difficult). Venture Manufacturing (
https://www.venturemfgco.com/rv-and-...-landing-gear/) used to supply Montana with landing legs and you might have them. They have all the parts you would want. But if Montana went to a different vendor for your HC, you should be able to find parts from them also.
Put a hydraulic jack on the side of the broken leg and lift the RV along with the other operable leg. Or you can use two hydraulic jacks, one on each corner, to lift the RV. Ne sure to chock the wheels to prevent any movement.