Why does Apple delete previously downloaded songs and say 'no longer in your country/region' on iPhone 16?

Same issue, same message here..my daughter had the entire Harry Potter series on cassette tapes. She took the time to make mp3 files of them and upload them to her computer and then iPhone. She was just starting to share those with her daughter when she upgraded to an iPhone 16.....all of those files are gone. It happened to me with audio files that I had made from actual vinyl. I can't tell you how many songs/artists have been deleted by apple because they didn't match the copies in the iTunes database.