Apple TV Screen

What is your model Apple TV? Identify your Apple TV model - Apple Support

It may not be automatic. If your equipment or settings can’t use HDMI-CEC, then you will have to manually select the matching input port on your TV (or AV receiver), as with any HDMI device. Did you switch the TV to take input from HDMI 2?

Set up your Apple TV - Apple Support

Can you try a different hdmi port or the device on a different tv?

Hard to suggest a reset if you don’t get a picture.