Hi Rainer,
If the B2 is asking you 'Are you sure?' after selecting 'Play Aux' then the B2 is not in Aux In mode. Try powering off the B2, waiting a minute or so and power on again.
On the first screen after boot up does the scrolling text show 'Source: Hard Disk'?
If the scrolling text still shows 'No Network' - using the front control go to the Maintenance menu and select 'Reset WiFi'. Then run 'Setup WiFi' again.
For the 'No Cd mechanism' try 'Reset CD' again.
Paul
Brennan Support.