I’ve ready the various posts relating to similar topics. I expert the library xml via File/Library/Export Library into the same folder that the Apple Music media files are stored. the resulting file is called Library.xml.
I’ve requested Roon to force rescan of the my entire library (a subfolder of which contains the Apple Music media files and Library.xml file.
I did not reboot my iMac yet because it really shouldn’t be necessary.
I would be grateful if you could help me solve this problem.