I am just adding my name to the list of people experiencing this. I have been in contact with Apple Support and expect my third call back next week. While they have been very helpful, we have not been able to make any meaningful progress and they do not appear to have knowledge of a wider issue (I am being treated as an isolated case).
As is the case with others in the thread, the symptoms are as follows:
- Initially an album was not syncing across devices
- After switching iCloud library syncing off and back on I lost my entire library on my Mac, iPad and iPhone and the devices are all stuck trying to enable library syncing. (The Apple TV library also does not sync)
- Adding or downloading music is impossible as the iCloud syncing does not successfully switch on
- The library is retained on the web interface and can be edited and changed successfully here
- In addition, my library is also available and working on Sonos and Apple Music Classical apps (that presumably use a different interface).
As others have noted, usual problem solving steps do not help:
- Switching library syncing off and on
- Signing out and back in to store
- Resetting network settings
- Erasing device and setting up as new
- Using VPN to test for IP blocking or routing issues
My conclusion is that this is an Apple server / account issue that their engineers need to resolve on their end. I can only hope that it receives enough attention and priority as Apple Music is useless to me at the moment.