It had finished downloading the upgrade and was showing on the screen that it might take around 90 minutes and will restart several times. When i left, the screen was sort of like windows 10 and was going through a progress of about 38%. I left it there while charging and went outside for dome work. Around 30 minutes later, I came and found it switched off. I tried to switch it on by pressing power button, the power indicator blipped 2-3 times but nothing happened. Please help me.