This generic error is usually caused by clicking on an expired link to reset your password.
For your security, password reset links are only valid for a short time after they've been sent to you via email.
Each time you need to reset your password, be sure you've clicked on the 'forgot your password?' link at sign in and received a new password reset email. The reset process should be completed within 12 hours of receiving the email (you can always repeat the process if needed).
If you're still seeing this error message even after following the steps above, get in touch and we'll get you sorted.