EC480 control panel 2015 Kingham

Hi,
We have been on hookup in Spain on a campsite for 4 days . Today the control panel switches itself off. I've switched it back on and within a minute it switches itself off.
I've taken it off hookup for now and the control panel has now stayed on.
Has anyone any thoughts or explanation why the panel should automatically switch off, could it be an automatic protection because the van has been on constant charge for 4 days?
Your help/ advice is welcomed.

Is it actually switching off (everything shuts down) or is panel simply going into sleep mode (pressing up or down arrow brings it back on)?

Thank you for your reply.
The on/off blue light always has remained on when in use and the screen goes blank, both on EHU or if running on the batteries (which btw are new and fully charged) even when the rest of the panel goes into sleep mode.

what is the voltage when on mains charge.is it cutting out as to over voltage.