Apple 4k TV output flickers on and off

Hello Zbmbz,

Welcome to Apple Support Communities. 

We appreciate the troubleshooting that you have completed to this point. Please try the steps as listed here to reset your Apple TV: Reset or restore your Apple TV to its factory settings - Apple Support

Reset your Apple TV 4K or Apple TV HD

1. On your Apple TV, go to Settings > System > Reset.
2. Choose a reset option:

• Reset: This option is the fastest way to return your Apple TV to factory settings. This option doesn't require an Internet connection.
• Reset and Update: This option returns your Apple TV to its factory settings and installs software updates. This option requires an Internet connection.

1. Keep your Apple TV plugged into power until the Reset process finishes. Then you can set up your Apple TV again.

Apple has recently released a tvOS update. Please use the steps as listed here to update your Apple TV: Update your Apple TV - Apple Support

Update your Apple TV manually

1. Go to Settings > System > Software Updates and select Update Software.
2. If there's an update, select Download and Install. 
3. Wait for your Apple TV to download the update. Keep your Apple TV connected and plugged in to power until the update is complete.

After the update downloads, your Apple TV will restart, prepare the update, then install it. When the update is complete, your Apple TV will automatically restart again.

Let us know if you have further questions.

Take care.