Inserted music by desktop doesn't play on phone

[Pitbullwub]

Hi,

I'm having trouble with some music I inserted in Spotify myself. I inserted it, using the desktop a couple of months back and saved it in a playlist. Next I downloaded the playlist on my Android phone (OnePlus X) and it worked marvelous.

However, I have a new phone now. It's an OnePlus 6 and now when I open the playlist it still shows the music which is in there, but it doesn't play. The name of the track is also not white but a bit faded. I checked the files, but they're still OK. As a matter of fact, I can still play the tracks, but only using the desktop.

Anyone knows what's happening here?

(I already tried to insert the music yet again using the desktop. Worked like it's supposed to, but I can still can't play the tracks on my phone.