Apple TV

Can you select the Apple TV as AirPlay destination on the Mac? Are you sure it is the correct Apple TV, if more than one appears?

Are you trying to use in-app ‘basic’ AirPlay, or AirPlay Screen Mirroring?

Are all devices on the same home network (and not split up by use of 2.4 GHz and 5 GHz band)?

Use AirPlay to stream video or mirror your device’s screen - Apple Support

If AirPlay or screen mirroring isn’t working on your device - Apple Support

Some apps or services do not support AirPlay, or block AirPlay. E.g. you can’t AirPlay Apple DVD Player.

Some web videos may show the AirPlay icon (automatically), but the specific video may not always be compatible with Safari in-app AirPlay.

At this time, I suggest that you contact the Apple Support team as your next best step:

Contact Apple for support and service - Apple Support

Welcome to the Apple Community.

Try restarting your network router and perhaps the devices involved too.