It sounds as though the battery disconnect solenoid is not closed or there is an open fuse or circuit breaker. You should be able to turn on the house batteries and 12 vdc circuits work without shore, generator or inverter power being turned on. Recommend you get the owners manual and check out the house (coach) battery bank disconnect wiring. Use a test light to check across fuses and circuit breakers if you cannot easily see one blown or tripped. If the over current protection devices are good then check the solenoid itself for proper operation.
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