Does your 2009 Montana have the remote control unit? The manual switches not working on units with the remote control is a well known problem. Put a new battery in the remote (which you obviously are not using) and try closing the slides.
Join the Montana Owners Club (MOC) at montanaowners.com for answers to anything Montana related. There are numerous posts (with the solution) on the remote control unit locking out the manual switch
If you don't have the remote control system then you likely have a 12V issue somewhere.