Not sure if this applies in Europe, but in the US I found the answer to this question. I had my audio cables connected to the wrong Audio In connectors. Once I moved them to the other Red/White RC connectors on the IN side, the sound came back. I had the electronic hum one of the other repliers had.
Hi, Bugshan and all
Most of the times, this issue is related to a bad connection or settings to adjust. With this in mind, I recommend you to check the following link in order to apply the necessary troubleshooting steps in order to fix this issue.