Radio, CD player, Navigation System MUTE

[nyko46]

I had my 2009 Mercedes Benz E320 Bluetec battery removed for two weeks and now my audio is mute. It changes and play CDs but no sound is coming from speakers. Also when selecting radio AM/FM a message: "device not available" is shown on screen. I could't find any help on "troubleshooting" of the "Monitor Manual" for this car.
Many replies suggest to RE-CODE the radio and I believe that this is the way to go.
My navigation system will show me all directions correctly but no voice coming from speakers. Today I called two Mercedes Dealers and using my VIN they could not find radio code o their system. One of them said to remove the radio because the code is on the back of the radio. The other said that the issue can be different and to bring the car to them to be taken care.
Any other idea in how to get it resolved without dealer? They are costly.
Thanks