Hello ppraeww,
Thank you for using Apple Support Communities. It sounds like you’re having issues with turning on iCloud Music Library. I’m happy to help. To start, I suggest making sure you’re following the instructions in the article below:
Turn on iCloud Music Library - Apple Support
Should the issue persist, I suggest force-closing the Settings app and restarting your iPhone:
How to force an app to close on your iPhone, iPad, or iPod touch - Apple Support
Restart your iPhone, iPad, or iPod touch - Apple Support
If you have not already, it may help to update your iOS to the latest version:
Update your iPhone, iPad, or iPod touch - Apple Support
If the above does not remedy your issue, you’ll want to contact Apple Support.
Take care.