Synced songs won't show

[jhoolia]

Hi I bought a song on iTunes, and I synced it to my computer ( mac ) and put it in my playlist. When I try to look after the song on my phone ( iPhone 6S ) it won't show, and when I try to play it through my computer to my phone it says "song unavailable, you can still start radio based on this artist" why can't I listen to it on my apple device and how do I fix it? All other songs are working fine.