Greyed-out playlist songs on iPhone 15 after syncing from new Mac

I have an iPhone 15 and a MacBook Air. I have many playlists on the iPhone synced from a previous Mac. Recently I accidentally deleted them and resynced them from the new Mac. But more than half the tunes are greyed out and I get the message “not currently available in your country/region”. Firstly, I’ve only ever used one region without change. Secondly, the greyed out tunes were never purchased from Apple, but were ripped from CDs which I owned years ago.

How do I fix this nonsensical problem?

[Re-Titled by Moderator]

Original Title: Playlists missing songs