If after getting an e-mail about unsuccessful payment, you try to update your billing details, but see the following message:
Oh snap! Your account has been terminated since we were unable to charge your card/PayPal account. Update your payment method to continue with the Rankz.
That means, your subscription already expired and there's no way to update details for it.
Alternatively you can contact our support team and we will assist with renewing your subscription right away.