This happens if the Keychain database is corrupted. So we need to get rid of old keychain database and make a new one. First go to System Preferences select iCloud. Click Sign Out button there and sign out. If asked to delete or keep stuffs, select Keep. If you only see Delete, then click Delete or OK. It is OK, you can reconnect to iCloud later. This is very important step.
Once you did that, click on Finder icon on dock. In Finder, hold down Option key on your keyboard, click on Go menu at the top bar and select Library. In Library, open Keychain folder. You will see many files there in Keychain folder. Trash them all.
Then restart your Mac and this will force your Mac to setup a new Keychain folder. If that didn't work, then you have to boot your Mac to Safe Mode and then repeat the above steps. To boot into Safe Mode, turn off your Mac, turn it back on and immediately hold down Shift key for 20 seconds. This will boot into Safe Mode.
Please let me know if that didn't work, so we can continue troubleshooting. Remember, keychain mess is not easy to fix, so it will take some time and few efforts to get it sorted.
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