1. Check that the HDMI cable is correctly seated at both ends.
2. Try disconnecting the cable and connecting it again.
3. Try another HDMI cable.
4. Make sure your TV supports 720p (Apple TV 2 Only)
5. Try the Apple TV with another TV
Apple TV 2/3
You may wish to try the following:
Press and hold the menu and the up button simultaneously on the remote for six seconds, the Apple TV should then begin to cycle through the various resolutions available to it at 20 second intervals.. If you see a picture appear up on your screen, use the remote to scroll down to the OK option and select it.
Apple TV 4
You may wish to try the following:
Press and hold the menu and the volume down button simultaneously on the remote for six seconds, the Apple TV should then begin to cycle through the various resolutions available to it at 20 second intervals.. If you see a picture appear up on your screen, use the remote to scroll down to the OK option and select it.