If you have multiple iOS devices or Mac/PCs that share the same iTunes account, you might have done content downloaded on one that you want on another device.
How to download itunes content you’ve already purchased to other iOS devices:
First, access the iTunes Store:
Now, choose the “More” menu in the bottom and choose “Purchased”
Now, browse to the song you want (ONLY SHOWS BY ARTIST NAME?!?)
Finally, click the “Cloud” icon to download the song from iCloud to your device:
Did that work??