I understand you're unable to add new music to your music library. I'd be happy to provide information that may help you resolve this.
Let's start by making sure you have iCloud Music Library enabled from Settings > Music. Here's a full guide on this: Get help with iCloud Music Library
If this does not resolve your issue, would you respond to the following:If you can't download, play, or access songs
First check iTunes to see if the song is ineligible for upload. Additionally, if you added the song to your library from the Apple Music catalog, it might no longer be available on Apple Music.
Check your Internet connection
Open Safari on your iPhone, iPad, iPod touch, or Mac, or a web browser on your PC, and go to any website to make sure you have a strong Wi-Fi or Internet connection.
If you can't connect to a Wi-Fi network on your iOS device, you can try using cellular data:
- Go to Settings > App and iTunes Stores.
- Turn on Use Cellular Data.
You might have to pay a fee to download over a cellular network. Contact your wireless carrier for details, and learn about cellular data settings and usage.
1. Do you get any error messages when trying to add music?
2. Is your Apple Music subscription current?
Thank you for using Apple Support Communities.
Have a great day!