iTunes - Can't play songs uploaded to Apple Music

Hi.

I have my personal music mixed with the Apple Music store songs. I use this functionality to sync all my devices with the same music library. The issue is that most of my uploaded personal songs to this service are not working anymore on other devices.

I created my library on my personal MacBook with Apple Music songs plus my own. I log in on my phone and sync the same musics to be available offline on that device. But when I try to do the same thing with my work MacBook, most of the uploaded musics stop working. The download stays in loop and then the song simply doesn't play.

Then I tried to understand if the issue was with my work MacBook. When I log out and log in again on my phone, the issue starts happening also on that device. The same songs are unavailable to play. I already created an entire new music library but the issue remains. The songs play perfectly on my personal MacBook and for a certain time on my phone. Can you help?

Thanks.