Error Code?

I have a 2014 Citroen Nemo van. I had the radio switched on and it had been working normally. I stopped to get some fuel. When I got back in the van the radio was on. I thought strange as you need to press the On button for the radio to work with the ignition key removed. I didn't think anymore about it. The next thing that I noticed was that the radio display shows 'Code Error'.
I have tried disconnecting the battery with no effect I have tried pressing the On and AS buttin also with no effent. Any suggestions