Check the following to see if this helps:
HOME>Settings>Factory>Enter Pin>Vehicle:
Aux Switching Mode: I have mine set to AUTOMATIC
AUX Auto Switching: I have mine set to HARMAN (with a 13 E70)
One reason Volume may not be available is because the signal coming in is not Analog...which would be an Android Monitor issue.
Oh, this assumes the Aux In was working before installing the Android Monitor. If it wasn't working before, then that is a vehicle issue...hmm
More info, see end of Page. 2:
https://www.bimmerfest.com/threads/c...m-zero.961683/