E 80 Chartplotter

[Sandy4]

We have recently purchased our first yacht and have been taking short trips getting used to the equipment on board. We have a Raymarine E80 chartplotter which started rebooting itself. I did a reset and this seemed to fix the problem. We went on a slightly longer trip and on the return voyage the same thing happened again, so I thought do a reset, it worked last time. Carried out the reset and now the screen is blank, none of the buttons work and can't turn it off except at the switch board. Any suggestions.