[Richard]

Ok, you need to make the air leak isolator apparatus. You can search for the threads, but in simple terms

Air line, tee with a 150 psi gauge, quarter turn valve, tee with a 150 psi gauge, air line. Disconnect the air line from the six pack and put the apparatus between the six pack and the afore mentioned line to the air bag. Crank the coach up, open the quarter turn, and let it come to ride height. Close the quarter turn.
Turn of the engine. Wait.

The gauge that leaks down will tell you if the leak is in the six pack or the air tank/air bag. Otherwise you are guessing. You will save yourself a lot of time, aggravation, and money by properly diagnosing this. If the coach stays up with the quarter turn closed, you know the air bag and tank are OK, and the problem is the six pack.

Your aux compressor may not lift the rear of the coach. It takes about 110 psi to lift the rear. Or the leak may be greater than the supply capacity of the aux compressor.