Unfortunately, I'm not familiar with the Solitude, but if the inverter is installed behind a panel, there is almost certainly a remote on/off switch somewhere inside. I saw a post on a Grand Design forum that the switch for other models is located "under the cabinet where the main panel is located". Not sure exactly what that means though. Also unfortunately, they don't always label them real well. It's usually a toggle switch and often has the brand name of the inverter like MAGNUM ENERGY or XANTREX on the surrounding faceplate.
Hopefully someone more familiar with the Solitude will chime in.