I upgraded to OS Catalina last week on my desktop Mac. When I now try to sync my devices (iPhone XR, classic 128 GB iPod) I get a list of songs that cannot be transferred because they are "not authorized to play on my iPhone, iPod, etc. Moreover, I just imported some new music that appears not to have synched over even after a couple of attempts. It's almost enough to make me want to go back to Mojave OS and iTunes!
Any suggestions for getting all of my music to synch?