Why won’t iTunes let me buy music?

I have a little over $36 on my account and I’ve been trying to buy a $0.99 song. I’ll click the price button (since I’m on mobile) and it comes up with the menu asking if I want to purchase the song like it normally does. I click the purchase button and put in my password as directed and hit Sign In. After a little wait, it shows the little Done checkmark signifying that my purchase has been approved and all, but the loading circle by the song spins for a little bit before returning to the price button, never downloading the song. I tried other songs to be sure it wasn’t just that song and it’s doing it with every song I try to buy. I’ve checked my music app and my purchased items on iTunes and none of the songs show up and money isn’t being taken from my account. I’ve never had this happen before. What’s going on and how can I fix it so I can buy music again?