New answers tagged address-book
If your contacts were connected to an account (e.g., iCloud or Exchange), you may need to re-authenticate after an OS upgrade. Go to System Preferences > Internet Accounts and make sure Contacts for the account you use is checked.
Not sure if this is really a good idea, but you can run this (as yourself, not root) in Terminal: launchctl unload -w /System/Library/LaunchAgents/com.apple.AddressBook.SourceSync.plist FWIW, I had the same problem and even after following the instructions in Tetsujin's link, turning off all Contacts accounts in System Preferences, logging out of iCloud, ...
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