You upgraded your FormsCentral account? Can you explain what you mean that you cannot use it, what is happening, when and where are you being redirected? Did you use the same email address for the upgrade as you used to sign into this forum? We see a lot of cases where users sign into FormsCentral with one email address but then use a different during the upgrade process. Check and see if you have another email you might have used for the upgrade.
Try signing out and back in again and let me know if you still have issues, your account does show as a paid level account now.