Can’t download songs with enough storage.

i just got suscribed to Apple Music and it is quite good. But, I’ve been having some struggles when it comes to download the songs. At first, I could add as many songs as i wanted to, and I was able to download them, and they did so!! But after some songs, some others couldn’t download, and I got enough storage for them. I really don’t know what’s happening but I need to get it solved because I’m paying for listening to music with no conexion and unfortunately i am unable to. I need help with my service.