Thanks for reaching out to us about this - we'll be glad to help 🙂
If you're still unable to see your Liked Songs folder, do you mind logging in to your account on another device and seeing if they appear there? If they do, then try performing a clean reinstall of the desktop app and see if that fixes it.
If you're still having trouble, then get back to us and we'll see what we can suggest next 😉
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Are you referring to a "Favorite Songs" playlist that you created, or the "Songs" library that is updated each time you use the + button on a song? If it's the latter, it's now called "Liked Songs," and can be found by going to the your Library tab (at the bottom) > Music > Playlists > Liked Songs. It will be at the top of your playlists and the cover art is a purple/blue gradient with a white heart in the middle.