The Ubuntu Software Center works completely independent from our website. We do not process orders from the Ubuntu Software Center.
The entire order process (including sending out serial numbers and emails) is handled by Canonical/Ubuntu.
For your privacy the Ubuntu Software Center does not share customer and order data (name, email, address, payment info) with developers.
Unfortunately this make it impossible for us to know who you are or whether you are a customer.
If you have problems accessing products purchased through their system then please contact the Canonical/Ubuntu team directly:
https://help.ubuntu.com/community/Pay
Also make sure the confirmation email from Ubuntu did not end up in your spam.