Matt gives good advice. This is likely a setup error, not a defect.
Regarding the front panel display [AUX--Volume--CD] CD in this case is the source for the main zone, and AUX is the source selected if you were to turn on zone 2.
So, if your CD is your source, double check the type of input your using from the CD player to the MX120 and select that in the on-screen setup menu.
Regarding the front panel display [AUX--Volume--CD] CD in this case is the source for the main zone, and AUX is the source selected if you were to turn on zone 2.
So, if your CD is your source, double check the type of input your using from the CD player to the MX120 and select that in the on-screen setup menu.