Apple TV Library Won’t Load on One TV

Is this about using the Apple TV box, or other Apple device,

or about using the Apple TV app on a third party device?

Is this about your library of purchased movies and TV shows from the iTunes Store, in the Apple TV app? Library in the Apple TV app - Apple Support

Or is this about Home Sharing? Use Home Sharing to share media from a computer to other devices - Apple Support

Verify that the active account matches. If the Apple TV user account is different, then it won’t load the same library, or maybe no library at all. That can easily happen if there are multiple user accounts on the device.

Set up multiple users on Apple TV - Apple TV box user guide - Apple Support

Add additional Apple ID accounts - Apple TV app user guide - Apple Support