If your ecobee account uses the same username/password combination as another website that has been compromised in a data breach, you will see this message when signing into your ecobee account.
In order to protect your ecobee account in these circumstances, your account will be temporarily locked until you reset your password.
You can reset your ecobee password via the ecobee app or via ecobee.com by clicking "Sign In" or "Sign in to your account" and then clicking the "Forgot password?" link.