Contacts from Address Book Disappeared I just installed El Capitan (I used to have Lion OS X), and I lost my address book. So I googled about it and I can restore them from my time machine. I did that but the file can't be opened in the address book app. What can I do to solve this? Thank you.
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.