On my old computer, I had the following setup:
- iTunes Folder containing iTunes Library.itl on my main hard disk (~/Music/iTunes)
- Music folder on a second HD where all the actual music files lived (I had checked "Keep library organized").
My new laptop has only one HD, so manually I copied the Music Folder (2) to the new HD and put the iTunes Library.itl, iTunes Library Extras and iTunes Library Genius into it (both from a time machine backup).
Opening iTunes brings up a blank library. When I open iTunes by clicking the app icon while holding alt, choose the library it says:
iTunes library is not valid. iTunes has created a new library and renamed the original to "iTunes library (damaged)".
(translated from German)
I am using Apple Music, too. Am I missing something?