On the left side of the Bus in the rear, the narrow electrical compartment should contain the box with the fuses you're looking for. On our formal '08 it was at the top of the compartment on the rear compartment wall, not the back of the compartment. Box is about 6x8". You'll need a small screwdriver to get the cover off. On mine, the CB diagram of what applied to which circuit was evidently not read by the Tiffin techs but if you use a meter you'll find your bad fuse.
2013 Tiffin Allegro Bus 43QGP
2011 Chevy Silverado 1500 Toad