Hi andy123!, i´m not an expert though i have been testing a lot of custom roms and even noticed that the viewpad 10s does have problem with reboot/startup, it seems that it does just turn off the screen (like standby mode or something..) but never powers down the whole system completly, and there is no way to get the screen on again, solution for this was for me atleast to hold down the powerbutton for around 4 seconds (force it to power down..) and when powering it on, do NOT press any button at all but than the power button, if you press volume keys at the side will make it to not boot.. it just stays off and the same goes with the back key, so keep your fingers right hope this help you
/Patrik
/Patrik