"http://pay.ubuntu.com/" does not work for me; how can I purchase "Stock Tracker" app?

[Walter Goedecke]

I have downloaded many apps from the Ubunutu Software Center. I did see one app that requires payment, Stock Tracker. I do want to purchase this, but I receive an error message:

OpenID failed

OpenID authentication failed: Invalid openid.mode: '<No mode set>'

When I attempt to access my account, it states that I purchased the software multiple times. Since there is no way to rescind any payment, I have to cancel my account, create a new one, and try again.

How can I purchase software other than the Ubuntu Software Center, since it does not work for me?

Thanks,
Walter Goedecke
<email address hidden>