How can I restore missing apps on my Apple TV?

I think my Apple TV is Generation 3

Identify your Apple TV model - Apple Support

Find your Apple TV model number - Apple Support

The legacy Apple TV boxes (2nd and 3rd generation) [A1378, A1427, A1469] (2010, 2012, 2013) have ‘apps’ as pre-configured for your country or region by Apple and the content providers. These ‘apps’ get loaded from remote servers when the device starts up.

When a content provider chooses to no longer support the legacy model, then that app gets removed. There is no way to restore that on the legacy models. You will need to get a newer model, to have support for that service again.

Re-add the app and also ensure you did not put it into a folder and of course scroll to the bottom of landing pages.

Every Apple TV HD & 4K device has an App Store, please use that.