Ignition protection switch

That is a 40 amp circuit breaker used instead of a fuse to protect your battery.  If you are able to run your appliances off the battery, then the breaker is intact.  If not, I would reset it.  

The circuit breaker has tripped.  Push the red lever under the cover so that the lever is under the cover and it should work.  Pressing the red button on top will manually trip (open) the breaker for test or maintenance purposes. Those are very nice circuit breakers.