Music app fails to select the correct library

Since the Apple store transferred all my data from a late 2015, 27 inch iMac in early October, I have had nothing but problems with my Music App on my new 24 inch, 2 TB iMac. Without exaggeration, up to today, I have been on the phone with Apple support for over 24 hours in numerous call to second level support.

To get to today, after picking up my new iMac that supposedly had all my old data loaded onto it, I had to copy to an external hard drive my extensive music library that has over 10,500 albums and 133,000 songs (all ripped from cds), delete all music from my new iMac, reinstall the mac os on the new iMac, import all music from the external hard drive and frequently call Apple support as whenever I open Music it defaults to a library that only has the U2 album that Apple forced on all iTunes users years ago. In this transfer process by the Apple store I lost album art on about 20% of my collection and over 980GB of data was put into System Data when it should have gone to Music on the new iMac.

By pressing Option then opening Music I can choose the correct library BUT it does not contain recently ripped cds. God only knows where they have gone. A few Smart playlists have disappeared too. Second level support has me change the path to correct library (the extensive one) but each time I turn off the Music app or the computer, the wrong (U2) library opens not the correct libray with all my 10,000+ albums.

I am running 18.1.1 Sequoia. The Music apps on my desktop, iPad Pro and iPhone X are not synching with Apple Music streaming service so synching should not be the source of the problem. When I connect my iPhone X with an Apple cable to my new iMac and try to synch my iPhone with my desktop, it does not pick up the recently ripped cds nor the current status of the contents of any smart playlists that should have had new ripped cds added to them. Even when I drag and drop albums on a non smart playlist, that playlist on my iPhone doesn’t update.

I am about to set what is left of my hair on fire out of frustration! Each second level support person is very patient but every proposed solution is ineffective. The Music app will not stay on the correct library, ripped cds do not go permanently into the correct library or smart playlists and my iPhone will not update to the latest added cds. None of these issues were present on my old late 2015 iMac which had an even more extensive library that I winnowed down when I got the new 24 inch 2TB iMac. I have lots of storage space an all my devices.

Any suggestions to help resolve these issues would be helpful.