Stars rating disappeared

[S77]

I have multiple playlists that contain at least 1000 songs each and I gave them rating stars over multiple years while I listened to them, and now the stars are gone. Not all of them, about half of each playlist. What can I do to get them back, if that is even possible?

P.S. It's the User Rating that I'm talking about.

[Artem]

Please, refer to built-in help