In case you are not aware, the jack fuses are not with the rest. They are in the jack controller box under the step up to the sleeping area.
I agree with the others that the issue is between the batteries and the distribution box. When the generator is on, you are getting 12V power from the converter, but when it's off, you get nothing because the power from the battery is interrupted.
My camper is very similar to yours, so I will be interested to know where the in-line fuse is. If you pull out the flat drawer right by the back door, you should be able to see the battery cables you can start tracing them.