iTunes problems

Was this purchased music from the iTunes Store, or downloads from Apple Music?

If it is iTunes Store purchases you must be logged in to the same Apple ID on the phone that was used to purchase the music. If it is Apple Music you must have a currently active Apple Music subscription to download it.

What do you mean it doesn't let you download? Do you see the music in the iTunes Store app if you tap More and then Purchased? or if you search for it, does it have a cloud icon?