Every 12 volt system in the coach on your motorhome is fused. I believe you should look at your circuit breaker panel to see if any of those popped out.
You can also drop a couple of screws and get inside the wiring and check the line side of the feed to the fan with a test lamp. If the ground connection isn't firm that may also be a point of failure.
If you do have a popped circuit breaker I expect that the fan may be a little aged and is drawing to many amps which causes the breaker to pop.
If you have a conventional opening, I might opt for a Fantastic Vent and go from there.