Have you checked for the presence of power at the drive motor, or are you assuming it isn't getting power because it isn't running? It is possible that the wiring is fine but the motor has burned out (although I doubt it), so I think I would determine that for sure. Assuming there is no power at the motor when the switch is pushed, the only choice is to debug the wiring and switches. On my (newer) van, that circuit is protected via a circuit breaker, not a fuse. The CB is plugged into a fuse socket, though. If there IS power at the motor but it is not running, then the motor will need to be replaced.
Don't forget that there is a second redundant switch all the way in the back of the van, on the left bulkhead (or, at least there is on ours). Maybe that one will work?
The only way to fold it up manually would be to disconnect the drive screws from the fronts of the seat bottoms. There is one on each side--you would have to disconnect both.
Edit: One more thought--if the motor is OK but the wiring is bad, you could hook up a temporary circuit and drive the motor directly. The polarity of the wires will determine the direction of motor motion.
Formerly: 2005 Airstream Interstate (Sprinter 2500 T1N)
Now!: 2014 Great West Vans Legend SE (Sprinter 3500 NCV3 I4)