You haven't indicated what rig and remote system you have, but if it is a Lippert based system, the following may apply. This has been discussed numerous times on the Montana Owners Club forum.
The Landing Gear and Slides only working with the remote control and not with the outside manual switches has been a topic of discussion here lately. When ours stopped working "zman08" directed me to a post that solved our problem. It involved removing the ground for the manual switches from the remote receiver and grounding it to the chassis.
Apparently there is a "failsafe" circuit to keep the user from using the remote switches and the manual switches at the same time. The failsafe will not provide a ground to the manual switches when the remote system is energized and will sometimes get "locked" in that position. That is what happened to ours.
I just moved the ground from the receiver to the chassis and everything works again. Some users have also needed to move the 12V+ line to a separate 12V source. You can replace the receiver module, but I think Lippert wants around $150-$200 for it and it will probably just fail again. Our rig is out of warranty so this was the best economical fix for us. I have included a couple of photos of where the wires are for the manual switches and where I moved the ground to.
Manual switch wires "To Manual Switches"
Where the ground was relocated to
