Can't add songs to my music

Lately I'm not able add songs or even download them (to listen offline) to my music. When I press the "+" icon it shows the message that it was added to my music, but then when I press the "cloud" icon to download it, the icon simply disappears, and then it goes back to the "+" icon again. Even when I try only adding songs to my iCloud library (without pressing the "cloud" icon, just the "+" one) the icon suddenly disappears and it doesn't add the music to my library, I tried everything but it didn't solve any problem yet, so I need help to solve this, please.