Hello slice455,
Thank you for using Apple Support Communities! I understand from the information you provided that the downloaded music from Apple Music won't play; I'd like to help.
While the following resource is for help with iCloud Music Library, it provides some relevant troubleshooting steps to try for this issue:
Get help with iCloud Music Library
Specifically, check out the section labeled "If you can't download, play, or access songs"
If you still have issues, force close the Music app:
How to force an app to close on your iPhone, iPad, or iPod touch - Apple Support
If the issue continues after that, check for, and install, any available updates for your iPhone:
Update your iPhone, iPad, or iPod touch - Apple Support
Hope this helps.
Best Regards.