You are going to need to do a restore via iTunes. This usually is caused by an update not installing correctly.
If have a micro USB cable (sold separately), you can restore your Apple TV from iTunes:
- Disconnect the power and HDMI cables from Apple TV. Note: If you do not disconnect the power cable before connecting the micro USB cable, you will not see Apple TV in the iTunes Source list.
- Connect one end of a micro USB cable to the back of your Apple TV, and the other end to one of your computer's USB ports.
- Apple TV (3rd generation) only: Reconnect the power cable to your Apple TV.
- Open iTunes on your computer.
- Select your Apple TV in the Source list, and then click Restore.
Your Apple TV will restore to its factory settings, and will also download and install the latest Apple TV software update. This process may take some time.
Do not disconnect any cables from the Apple TV until the restore process is completed.