Welcome to the Apple Community.
First try restarting the Apple TV by removing ALL the cables for a 30 seconds and then try to reset.
If your problem persists get yourself a micro USB cable (sold separately), you can restore your Apple TV from iTunes:
- Remove ALL cables from Apple TV. (if you don't you will not see Apple TV in the iTunes Source list)
- Connect the micro USB cable to the Apple TV and to your computer.
- Open iTunes.
- Select your Apple TV in the Source list, and then click Restore.