Mac Messages notifications are only displaying phone numbers or email addresses after upgrading to Ventura

I just upgraded my mac from 10.14 to 13.6.5. Now whenever I get a message, the notification that appears shows the person's phone number or email address rather than their name. My contacts are synced using iCloud, and the notifications work fine on my iPhone. It was working just fine in 10.14 too. Any ideas on how to fix this? Update: I tried to fix it by signing out of Messages and signing back in again... and now every single one of my iMessage conversations are gone! 😭 All of my SMS messages are still there.