Good afternoon Todd Templeton,
Welcome to the Apple Support Communities!
I understand you updated to macOS Catalina, and the Music app is not showing the Apple ID that you were using for the iTunes Store and your personal music library. Does your personal library show all of the music that you had previously? If so, try the steps below:
- Sign out of your account.
- Quit the Music application and restart your computer.
- Sign in with your current Apple ID.
- Try to play the same song and one or two other older songs to see if the issue persists.
What happened to iTunes?
Sign in with your Apple ID
Authorize or deauthorize your computer for iTunes Store purchases
Please reply to this thread if the issue persists after trying the steps above, and I'll do my best to help you with this!
Take care.