Contacts are the most sensitive and useful data apart from iMessage, Mail, and Notes. So Apple always cares about your contacts under top security for no loss in any case, and it will. In case due to some wrong configuration and past data history in the contact app, you might see unexpected behaviors on the Contacts app on Mac, especially after upgrading your Current OS. Right now, many users have a problem with upgrading to MacOS. LEST noted about contact app’s wrong behavior or Contact App not working on Mac.
Note: Keep a backup of all contacts by Exporting contacts from iCloud before you proceed, and for future times restore it again or for privacy.
Steps for Repair or Reset Contact App on Mac
Step 1: Go to the Finder, click on Go Next, Go To Folder… on Mac.
Step 2: ~/Library/Application Support/AddressBook Go to the Command like on your system, System path for folder location. Copy the command on finder.
Step 3: Click on the AddressBook folder. You will see the three files below.
Step 4: Select all three carefully and Move to Trash (By right click on it and Choosing to Move to Trash)
Start contact app, it will automatically re-index all the contacts after syncing successfully. Now you experience a properly configured contact app on your Mac system.
If you did backup your Mac on Time Machine, try restoring it from Time Machine. Many recovery tools also help to fix this issue (Buy unexpected delete operation for your contacts).
Note: Same for iOS devices. You might lose or hide all contacts app in contact iOS app by changing the group. Here’s the fix on Unhide or find saved contacts in the Contact iPhone app.
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