Thank you all for great answers. I had the same issue. Nexus 7 2nd generation almost brand new and fully charged was not turning on. I tried to charge it for an hour then for 10 hours and hold the power button for couple minutes. Nothing helped.
I have followed the steps at
[guide|16072]
and opened the back cover. Disconnected battery for few minutes and once I put it back together, the tablet booted up with no issues.
Once again, the interweb has saved the day.