New nexus 7 tablet locks rotation - any way to reset without a reboot?
Rebooting into Safe Mode fixed the issue for me somehow.

To go boot into Safe Mode:


  1) Long Press on the power button for 1 second.
  
  2) in the power off menu that appears, press and hold the Power Off option.
  
  3) A Reboot into Safe Mode dialog will appear, Click Ok to boot into safe mode.


After you have booted once into safe mode, check if your auto rotation is working. If it is working then good, reboot normally. If not, then it is most likely a hardware issue and get your nexus 7 replaced/repaired by Asus.