Cannot connect MacBook to Apple TV

Ok, your 2nd gen Apple TV is AirPlay, not AirPlay 2 compatible. Regardless, you should be able to stream to it from your MacBook.

Are you trying to mirror your MacBook's screen to the Apple TV or stream a video to it? If the latter, where is the source of this video? On the MacBook or from the Internet?

Finally, can you ping the Apple TV from the MacBook? In order for AirPlay to work, both devices need to be on the same network subnet. See if the following article can help: If you can't use AirPlay or mirror your device's screen - Apple Support

Which exact models are your MacBook and Apple TV and which versions of macOS and IOS are they running?

For reference, the following are AirPlay system requirements: AirPlay system requirements - Apple Support