Songs added in playlist from desktop doesn't show in iPhone

[emmyandersson]

Hello! 
I'm not sure since when, but I guess in the beginning of June or something, the music in my playlist isn't there on my iPhone. When I use my laptop it says 59 songs, and on my iPhone it says 48. 
If I add a song from my iPhone, it shows up, but not when I use my computer. This is really annoying, because I want to listen to my music. 
At first I just thought it was loading slowly, but apparently not. 

Any solutions to this problem? Anyone else who has this?