If you measure 12 +vdc at the cables on the battery, follow the positive cable back to the fuse block and check the connections and fuse. Make sure the battery disconnect is turned on and that current does flow through it. Good luck and keep us posted.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7