Huge music library suddenly empty after trying to switch to another library - backup from Time Machine does not fix
Today I launched Music on my Macbook Pro and decided to try using multiple libraries. At this point the laptop's library looked normal.
I copied the Music Library from my iMac to my Macbook Pro, gave it another name and put it in the Music/Music folder. The content for both libraries (one lossless, the other lossy) is on the same remote HD, connected over wifi.
After disconnecting my iPhone and iMac from the domestic wifi and restarting the Macbook, I could choose the copied iMac library by holding down option, but when it came up it was an empty library. Oh well, I could research that problem in due course, but nothing lost so far.
I option-launched Music again and selected the Macbook's own library, which was fine 10 minutes earlier... and it was also empty.
What???!!!! That's the work of more than 20 years of organisation that's disappeared.
No need to panic. I have Time Machine. So I restored the Macbook library file from a backup earlier in the day (the modified date was months earlier as I hadn't added to it in a while).
I launched Music with only that library in the folder, fingers crossed.
Still empty!
I restored the whole Music/Music Folder from a Time Machine backup.
Still empty.
I restarted.
Still empty.
I've searched these forums and found lots of people have lost their Apple Music libraries, but not like this, and not when a backup file doesn't fix the problem.
Can anyone offer me any hope?
MacBook Pro 15″, macOS 10.15