Where is rear view camera fuse?

Got a Swift Lifestyle 624 built on a Fiat Ducato with a Swift installed 2-channel camera display unit instead of the central rear-view mirror. Rear view camera comes on automatically with ignition and automatically switches to downward facing camera when reverse gear engaged. Until yesterday I've never even touched it because it has always worked automatically every time. But yesterday when I started the engine the display was dead. I tried pressing the on/off switch and the various other switches. Nothing. I'm hoping it is just a fuse. But where is the fuse? Swift manual says the fuses are in the habitation area fusebox Power Supply Unit. I've studied them but none are labelled camera. I've taken each fuse out and checked it, but none have blown. Does anyone know if there's another fuse somewhere else? If not, has anyone got any suggestions? The cable goes direct into the display unit so I can't unplug it to test continuity. The cable is not easily accessible once it goes into the roof above the passenger. I'm going away in the motorhome in a couple of days and I can't get anyone to look at it before I go and I'd like to have it working for the trip. Any help/advice would be much appreciated. Thank you.