Could be that your Windows was in some system update process and you have interrupted it? Now, while powering on your NUC can you see Intel logo and F2,F7,F10 menu? Your O.S. is Windows 10?
It's not a windows problem since the NUC is not even posting and there's not output to any of the displays i used.
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Is it possible for you to try with different power adapter?
Press and hold the power button down for 3 seconds, then release it. If you get a menu screen with the options to access the BIOS try to see if you can set the BIOS to default settings by pressing the F9 on your keyboard and then press F10 to save all changes.