I would guess you've got a few things to check. First, the terms usually used are 'House' and 'Chassis.' The house battery(ies) power all the interior living circuits, including interior lights, furnace, thermostat, water heater, etc. The chassis battery(ies) start the engine, dash controls, wipers, driving lights, etc.
Your reference to 'auxiliary' battery I'll assume is the house system. Usually the cable from the battery goes to a solenoid that is an isolation switch to disconnect the battery during storage. The switch for this Battery Isolation Switch (BSI) is generally near the entrance. It's a double throw, momentary contact switch to 'toggle' the solenoid connect/disconnect. Near that solenoid is usually a large fuse that blows for safety if the large cables get cross connected. Check that fuse, (or circuit breaker) to see if it's blown. A multitester or test lamp could be used, if it's a fuse and blown, replace with the same size fuse.