Sounds to me your battery isolator solenoid is gone, same thing happened to our 04 Atrium, the solenoid in ours is located right rear elect compartment second from the rear, ours was powered up and clicking but no power transfer through it, ours was powered all the time and we are expecting the Intellic controller in the front left side compartment is faulty also, have been told the fail hand in hand. How I diagnosed mine was when the engine was running and the solenoid was engaged I checked my voltage on both sides of the solenoid, chassis side showed 14.5 volts and house side was only at 12.5V when engine is running they are supposed to be the same, should both be 14.5v! They have a couple choices for the isolator solenoids, a 200 amp & a 500 amp, I would recommend the 500 amp, this solenoid is also for tying your batteries together with the switch on the dash for emergency start, when you are trying to start a diesel engine it takes more then 200 amps so a 500 amp is more durable.
Hope this is some help to you.