This proble is fixed as I confirmed. Now paying through checkout.minecraft.net won't tell you that this is "Invaild Request".
Many Chinese players have reported this problem. They used Alipay pay method and met the same error.
Mojang should consider this problem highly, rather than setting the priority to normal.
Some Chinese character have this problem too
Weedy CN
This proble is fixed as I confirmed. Now paying through checkout.minecraft.net won't tell you that this is "Invaild Request".