It looks like you've attempted to sign in using an old password. If you remember changing your password, just sign back in using your most recent password. If you remember changing your password but have forgotten your new one, you can regain access to your account by going to our password assistance page.
If you don't remember changing your password, someone else might have accessed your account and changed your password. In some cases, your previous recovery email or phone might be available on the password assistance page for resetting your password. If that's not the case, you'll have the option to fill out our account recovery form to verify your identity and reclaim your account.
To show this message, Google needs to store your old password (actually, a password hash, since Google doesn't store the actual password). This is probably useful if someone managed to access your account and changed the password. Obviously, you'll still try the old password and you won't understand why it no longer works.
