Upon checkout you need to confirm the sale via a email sent to the email address provided by you.
I may be the exception and granted - it's basically due to a very crappy phone on which email ceased to work - but I was not able to finalize the sale since I'm not able to access my private email remotely.
I sent myself the link and will probably give it another shot from home. But you may want to take it up with the seller that there are folks out there for which this is not really a convenient way to close a sale. Especially not after entering valid credit card information.