Have had that problem myself when flashing Android
when its turned on and you see the dnx mode, hold down the power button for 30 sec, even when the screen turns off, keep pressing untill the 30 sec have gone, after that you should be abel to boot normal again, worked for me
I tried that but now the tablet doesn’t boot anymore. The screen won’t turn on. Pressing power button makes the power led turning on for two – three seconds, than goes off again, and nothing else happens. Also tried with power cable attached but nothing. Anyway, if attached to the power the led light keeps flashing. So something inside is still happening. Maybe it’s just run out of battery? Il try keep it plugged in for a while and see what happens.