I have the same issue.
Sometimes the power button does nothing, sometimes it works.
However, I have an old HP media center remote control (TSGH-IR01 ; FYI, I see these used on Amazon for 10$) I found in a drawer, that does wake it up.
So when the power button does not wake it up, I use that remote control to wake it up.
I haven't tested if disabling the CIR stuff in the UEFI resolves the issue since I'm not bothered that much.
FYI, I had no such issue on Windows 8.1, only on Linux (4.0.x).
I had this same problem recently with my NUC5i5RYH.
The only sign of life was the link/activity light on the Ethernet port.
The power button did nothing.
I read on this forum that you can use a Wake On LAN utility and send a magic packet to wake it up.
I tried that and it worked for me.
So, I took it apart and pulled the CMOS battery for 60 seconds. Back alive. Still trying to make up my mind whether I want to RMA (or trash) it. Never had so much trouble with a piece of hardware. At least it shouldn't be hard to send it back in a bricked state...!
Today, the same problem has happened again twice. BIOS is on defaults (I have dialed down fan speed but that's it).
Thanks for the tip about WoL - that's good and works to resume when this happens. Do NOT pull the power cord on the NUC! I don't have an IR remote to try.
Before flashing the latest 0247 BIOS I didn't have a single case of this problem (or even knew about it). After flashing, now 3 cases of the power button unresponsive in less than a week. First time practically killed it. I plan to flash back to an old BIOS version before the suspend "fix" and see if that helps (hope I can go backwards with BIOS versions!). I am running 14.04.02 LTS kernel 3.16.0-38-generic #52~14.04.1-Ubuntu SMP 64-bit FWIW.
Very disappointed with Intel on this - they seem to think it's fixed or don't care?
Had another two power button failures today alone. Without the WoL hack, I'd have defenestrated it.
Finally had the chance to downgrade the BIOS to 0246 which is the version immediately before the suspend "fix" - I'll see if this makes any difference. I could not downgrade all the way back to 0132, which was a bit alarming.
Thanks Allan. I will return it to the retailer here in the UK.