Connected on WiFi but no sound

[Jean-Marie]

Did you check what is selected in iTunes as your speaker output? Should be "Computer Devialet Air".

Do you mean the output device under the OSX general Sound preferences, or is there actually somewhere in iTunes you can select output device?

I think it is the general OS X output from the system preferences. 

I believe this is a bug in OS X which sometimes obliged me to explicitly select the virtual sound card. After an OS upgrade or a fresh install of the virtual sound card. 

I have also encountered a same behavior with a USB DAC which makes me believe that this is an OS X issue. A minor since after that one manipulation it is good even after restarts. 
Jean-Marie