If you need to update your keychain password on Mac
Your login keychain password is normally the same as your user password (the password you use to log in to the computer). At login, if your keychain password somehow differs from your user password, it doesn’t automatically unlock, and you’re asked to enter the keychain’s password. It’s recommended that you enter your previous user password. If this doesn’t unlock the keychain, the keychain automatically resets.
If you don’t remember your previous user password, you need to reset your default keychain. Resetting the default keychain deletes all the passwords saved in the keychain, but lets you sync your login password and the password stored in the keychain.
To do this, change your password in Users & Groups preferences, and the keychain password is automatically changed to match it.
Note: It’s recommended that you manually reset your keychain only when advised to by Apple Support. Resetting default keychains requires you to log out and log back in to your Mac to complete the process.
In the Keychain Access app on your Mac, choose Keychain Access > Preferences.
Click Reset Default Keychains.
Choose Apple menu > Log Out. When you log in again, save your current login password in a keychain.
If your user password was reset because you forgot your password, and you can’t provide the old password for the keychain, you won’t be able to access the information in the old keychain, and a new blank keychain is created.