I owned two Montana's. Both had the artic pak which was heated holding tanks
(if the switch was turned on.) Extra installation? Can't answer that one.
Did I read in the post down a ways the batteries were disconnected? My slides ran off the batteries which had to be connected (or turned on.) If I felt the batteries were not up to full charge, I would plug the cord from the fiver into the truck, start the truck and let the truck give some charge to the batteries in the fiver to pull the slides in. Never failed me.