I have updated my NUC 7i5BNK bios to 2017-5-18 ver 0047
and find that the power LED out of work. Both <button> and <ring> LEDs will keep black when set to Power S0, and both LEDs work when set to HardDisk.
Before BIOS update, Power LED works normal.
If anyone have the same problem, do let Intel knows.
I solved this problem by re update BIOS again.
Poor me for not understanding what had happened within the first time BIOS Update.