login problems

As per this article : Change or reset the password of a macOS user account - Apple Support

Create a new login keychain

After resetting your password and logging back in to your account, you might see an alert that the system was unable to unlock your login keychain. This is expected, because the passwords for your user account and login keychain no longer match. Just click the Create New Keychain button.

If you didn't see an alert about your login keychain, or you see other messages asking for your old password, reset your keychain manually:

1. Open Keychain Access, which is in the Utilities folder of your Applications folder.
2. Choose Preferences from the Keychain Access menu, then click the Reset My Default Keychain button in the preferences window. After you enter your new password, Keychain Access creates an empty login keychain with no password. Click OK to confirm.
   If you don't see a Reset My Default keychain button, close the preferences window and select the “login” keychain from the left side of the Keychain Access window. Press the Delete key, then click Delete References.
   
3. Choose Log Out from the Apple menu to return to the login screen.
4. Log in to your account using your new password. Your account password and login keychain password now match again.

When you create an Account for the first time, the password for your user-Id is used for the initial keychain login password. As you create more passwords and other items, anything that could be synchronized with your iCloud keychain gets added to your local items keychain. You never get asked for another password and all is well.

If you change your login password, and especially if you force-change your login password, the keychain password(s) sometimes do not get updated correctly. When this happens, you will get these request(s) to unlock them.

To fix this, your should launch the Keychain App and change the keychain passwords for login and local items keychains to correspond with your current login password. You will need you OLD password to do this. If you cannot provide your OLD password, these keychains will be dead to you, and you will have no choice but to create new, EMPTY keychains for the items, and build them back up as you go about your business.

Some users will protest, "But I do not use keychain for anything!" My answer is that if your email password does not have to be entered each time you start Mail, you do indeed use Keychain.