Apple Tv app shows only library

Either you signed out of the account,

or you (or your Apple ID account) are in a region where Apple Media services are not available,

or there is a region conflict,

or your Wi-Fi doesn’t provide internet access,

or the TV app is in error, and the app and device need to be restarted.

Then that is the reason, as only synced videos are available in the Tv app for that location.

Where are you located?