The password for your account may not match the password that is used to unlock the keychain. This can often happen when your password is changed outside of the operating system itself. To correct this issue, you can either create a new login keychain or reset the password of the existing keychain.
Apple has created an article to walk you through the steps on resetting your keychain password. https://support.apple.com/guide/keychain-access/if-you-need-to-update-your-keychain-password-kyca2429/mac