Do you see any LED color on the power button?
I just met with exactly the same problem but with two minor differences : 2 operating systems could be selected at boot : either Windows 7 pro in UEFI mode or Ubuntu in lagacy mode, and the NUC is nearly 2 months old. The bios has been updated thre's less than a week from release 130 to release 249.
And to answer the question, now there is no LED color on the power button. But the NUC seems to be powered as evidenced by the flashing green LED near the network connector.
No, power button LED does not illuminate - it looks completely dead.
It appears others are randomly having this problem with Ubuntu and S3 suspend state.
At the moment I'm calling it a BIOS error, because no matter what Ubuntu does it should not brick the NUC.
Incidentally I installed latest BIOS (0249) before installing OS.
Power supply is OK (there is a green LED lit inside NUC, but nothing on switch).
I have submitted a support request.
The more I read about this issue, the more I am convinced there is a BIOS issue.
I accept the possibility that Ubuntu might not be going through correct process while in S3, but that should not brick the NUC.
I am wondering about Intel support on GNU/Linux : see https://communities.intel.com/thread/55847?sr=stream Do you know what are "prefered distros" for NUCs ? I am asking, because I am facing issue since I upgraded DE3815TYKE to latest BIOS , It's affecting debian, archlinux, tizen too and want to make a proper report about observed regressions...
Being again faced with the same problem, but with a new NUC5i3RYH, I just found a workaround. To unlock the NUC, simply send a wake on lan to the NUC.
This is one of at least fourteen threads in this forum which address Intel's 'Linux Suspend > Dead NUC' intermittent defect, dating back to August 2014.
The good news is that a workaround exists which means you can at least avoid getting your NUC bricked by this defect, and it involves using methods other than a short press on the Power button to wake a sleeping NUC – ie: wake-on-USB and/or wake-on-LAN.
For full details, see the 'Workaround Alert' above the my OP in the 'NUC5i5RYH Bricked by Ubuntu Suspend for Fifth Time' thread » https://communities.intel.com/message/359708#359708
Thank you for the information provide regarding this workaround.