Sorry, my Englishi is poor.
I have installed win10 in my NUC8, then I installed linux in other partitions. After that, I find that I can not enter linux or bios.
After searching in google, I think my bios is broken, so I download a new bios in my usb stick.
However, even I press the power button for 3 seconds, I can not enter the power button menu.
I don't know why.