You should have received an email notification to let you know about your recently failed payment - this email will contain a link to update your billing information. If you can’t find it, or want to update your details via the site, head to Account > Membership Details, or follow any of the links to Upgrade.
Once you've updated your billing information, we'll try processing the payment again. Once your payment is successful, we'll sent a confirmation email and your Pro membership will reactivate automatically.
You will be given 2 weeks to update your billing information before your subscription is closed. After this you can upgrade again to start a new subscription.