When a user’s login keychain does not unlock automatically when the user logs in its because the keychain’s password does not match their account password. The user is prompted to unlock the keychain but if they have forgotten or do not know the password the prompt will appear every time an application or service tries to access the keychain.
Changing your account password in the Users & Groups preference pane will automatically update the login keychain’s password. However, if an administrator changes the password for an account other than theirs or if the Mac is bound to a network directory service and the directory account’s password is changed, the user’s login keychain password will not be updated.
Fixing this problem can be done in one of two ways.
Another keychain, Local Items, may not unlock when a user’s password is changed as described above. In that case, the way to fix the problem would be,
- Log in to the user’s account.
- Click the Go menu -> Go to Folder… (⇧⌘G).
- Enter ~/Library/Keychains/ then click the Go button.
- Delete the folder named with the computer’s UUID, which will be something like, 123E4567-E89B-12D3-A456-426655440000.
- Restart the Mac.
The folder and its contents will be recreated automatically and all should now be well with the Mac and the world.