Mac – Can’t sign in to Apple Music, TV or Podcast on Mac

I bet it is because she had iTunes Match. My father and I are both having the same problem and both of us has iTunes Match, but no one else is having problems with it.

As I suspected, once you turn iCloud library on, it is reluctant to allow you to add music using iTunes alone, as there could be file duplicates and a storage war.

Per Apple's forums, turning off iCloud musing will allow you to sync music manually, then you can turn it back on. Note this will delete all the 'iClouded' music and then re-download it, you you'll probably want to do this when you have a spare hour or so and a stable wifi connection.