Yep, sounds like either the main disconnect or the salesman's switch is turned off. Use your multimeter and trace it down starting, as you did, at the batteries.
Ron, Sandie and Lilly
2013 Tiffin Phaeton 42LH 400 ISL | 2011 GMC Terrain SLT-2
Roadmaster All Terrain | US Gear Unified Brake System | Pressure Pro