Why can’t I download songs from iTunes Store?

This has becomes very frustrating to me and I can’t find a clear answer to help solve his problem..

When I go into the iTunes Store to download a song I am unable to download the song and it show up in my iTunes library..

once I hit download it starts the download but right at the end it stops and goes back to asking me if I want to download it again..

I have checked my wifi connection which is working, I’ve restarted my phone and shut it down and that has not helped. I have checked my settings and nothing seems out of place. Please someone help me understand what’s going on and how I can fix it