If yours is a Roadster and you (like me) wash your car with the top down, water can trickle down onto the connectors on the top of the tank. I had this issue about two years ago with my Red one. Fixed it by cleaning the contacts with Q-tips and rubbing alcohol.

It's bedtime so I can't check now, but I don't think there is a separate fuse for the gauge.

May be a bad sending unit in the tank. I have no idea how to access it in a coupe, never owned a coupe.