when i download music from itunes, it does not appear on my phone but it does appear on my ipad. i can't download from the cloud to my phone either.

When I download music from iTunes using my iPhone 5s, the music never appears on my phone. It does appear on my computer and my iPad, but not the phone from which I downloaded the music. It appears in Purchased from the store, but I still cannot download it from the Cloud to my phone. Any thoughts on what might be causing this?