After each step, see if your issue has resolved.

1. Unplug both ends of the HDMI cable, then firmly plug them back in. Or try using a different HDMI cable to see if the cable causes the issue. Then in the television menu, make sure that you select the HDMI input that matches the HDMI port connected to the Apple TV. 
2. Unplug your television and your Apple TV from power, then plug both back in.
3. Try to restore your Apple TV.
   

• Try a different HDMI port on your television, starting with HDMI 1 or Input 1.
• If you see the Apple logo and then a black screen, hold Menu and Volume Down for 6 seconds, then release. Your Apple TV will switch to a new resolution every 20 seconds. Select OK to choose a resolution or Cancel to quit.
• If you're using a receiver or an HDMI switch, one of these might be the issue. Connect your Apple TV directly to the television instead of using the receiver or HDMI switch. If you now see the Apple TV Home screen, connect your receiver or HDMI switch one at a time. After each additional device is connected, check that you still see the Home screen on your television. 

If you still can’t see a picture on your television, hear sound, or only see the Apple logo, contact Apple Support.