For what it's worth, I have a '15 Berkshire with a residential refrigerator and the ice maker/water in-door. When I got it it didn't have water flowing and I started searching for the water line. As it turned out, the line ran all the way across the bottom of the rig so initially I couldn't find where it tied into the system, let alone a shut-off valve. After checking with service at the dealer, who couldn't help, I went on this forum. found out they have a shutoff under the bathroom sink, fully on the other side of the unit.
If you discover that there actually is a line run to the refrig, check out ALL the possible places in the plumbing to see if there's a hidden shutoff.
2015 Berkshire XL 40BH
Toad 2015 Chevy Equinox LTZ V6