If you have already paid for an account and are being asked to pay again, you may have two accounts - a paid account, and a free account. You'll know you are accessing a free account if it says 'Upgrade' in the upper right.
The solution? Log out of your free account, and try your alternate email addresses! If you are still unable to locate your paid account, send us an email at firstname.lastname@example.org and we will be happy to help.