NBA App

No. The older models have server based channels and providers have been dropping support for those versions steadily for some time. The 2nd gen is over 10 years old and was classified as obsolete years ago, the 3rd gen is over 8 years old and while Apple is still supporting it with a server version of their TV app and subsequent basic firmware updates 3rd party support is dwindling.

If you have an older Apple TV (2nd or 3rd gen) then it doesn't run apps. You can check settings - main menu to ensure it hasn't been hidden. Otherwise it may be that the provider has dropped support.

If you have a current Apple TV HD (4th gen) or 4K (5th gen) then do a search to ensure it hasn't been moved or you can go to the app store to download it again.