Unable to import .abbu file into Contacts on Mac OS Big Sur 11.6.1

Were the contacts local to your Mac or on iCloud?

The backup would only restore your local contacts (if it even works).

When Apple switched to using XML files for the contacts instead of vCards, the XML files wouldn't import.

The abbu is just a copy of the AddressBook folder and that is replaced when you "restore" it. I have not seen it work, but have not tried in years since all of my contacts are stored in iCloud.

I have never seen the AddressBook backup work to restore. I was hoping it would be fixed, but it apparently hasn’t.

I have suggested they remove the backup option and just leave the vCard export so people could at least recover the contacts.

You can go into the backup package and try to double-click the XML person cards to see if they will import. Ctrl-click on the abbu and choose show package contacts. The person cards should be in the metadata folder.

Everything should be contained inside the AddressBook folder, but it appears something outside of it is reverting the changes when you restore. That could possibly be the app Container, but it points back to the AddressBook folder with an alias and doesn’t maintain any data.

The container is ~/Library/Containers/com.apple.AddressBook, but may show in the Finder with the name Contacts. Delete that, restore the abbu, then open Contacts.