Apple TV not restarting after a power cut. How can I reset the box?

Please unplug it from it's power source for 2-3 minutes and then retest it. If that does not help then we need to know which Apple TV model you own, in that case please use Identify your Apple TV model and once we know the model we can give you further direction.

If the force reboot does not work, as suggested above, then you will need to take the unit into Apple