How to pay, I goon get a PRO.
We are unable to accept your payment or order. There may be many reasons for the situation of Sao.
To help you complete this order, please contact us for assistance.
(I used Copyfish to translate the screenshot)
Based on this info, I can not tell you why the order failed. Best will be if you ask Fastspring directly. Fastspring is your payment provider.
Fastspring support: https://fastspring.com/question-a-charge/
Then, on their website, select the “Pre-Order Questions” and then “Trouble Purchasing” from the drop-down: