Hi nwiber,
The vacuum turns on when you plug the hose in. You'll notice a metal ring around the end of the hose. That makes contact to provide 12V to the relay in the vacuum, which in turn activates the 120V AC motor.
If it's not working, check the 120V AC circuit breakers. Flip off and back on. Check the 12V DC fuses for a blown fuse. You may have to verify that the vacuum is plugged in. Unfortunately, that's probably behind the rear wall of the pass through storage.
It could be due to a stuck relay inside the vacuum, or to a disconnected wire. But check the easy things first.