I have a Sony Bravia TV which has been linked to a Panasonic sound system for a few months now without problems. However two days ago things changed. When selecting the audio system instead of TV speakers, the audio system turns on and automatically selects 'AUX' instead of 'ARC'. The end result is that there is no sound.

The TV is connected to the sound system by way of an HDMI cable which on the TV is marked as 'ARC'. I didn't move any cables so I can't fathom why it has changed. I can manually change it to 'ARC' but that also doesn't make the sound work. Does any one have an idea of what I can try to make it work again?

Thank you