Apple music can't locate some music files
I have had a mix of music from the iTunes store and from CDs loaded to iTunes over the years and have played it successfully on several generations of devices. Now, much of that cannot be found by the Music app on my iPhone, iPad or Mac. Those "unable" albums appear on the iPad and Mac (not on the iPhone) without artwork and the songs appear when I open the album but when I try to play something I get a message of:
The song “(name of song)” could not be used because the original file could not be found. Would you like to locate it?
I click on Locate and the Finder opens but no song is located.
Any suggestions for finding my "lost" music?
iPhone 12 iOS 14.2.1, iPad 2018, iOS14.2, Mac Big Sur
iPhone 12, iOS 14