Hi Robin. Welcome to justanswer.
May I know how did you transfer the Amazon music files to your phone?
Do you have Amazon Prime music app installed in your phone?
Try refreshing the library again
Do you get any specific error when you try to play the songs?
Go to play store and search for this app and see if it is updated or not.
Yes uninstall it from your phone then install it again. Log in with your credentials and see if it works or not.
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