ISSUE
After entering my credit card details and clicking "continue," the steam window closes, and then reopens showing my library, without completing the purchase.

OS
Windows 10

STEPS
Add a game to my cart.
Navigate to my cart, and click on "proceed to payment."
Enter credit card details.
Click "Continue."
RESULTS
The Steam client window closes. A few moments later, it reopens, but shows my library. The game is still in my cart and has not been purchased.
If I click on "Store" in the menu bar, the Steam client displays a black page with the URL "data:text/html,%3Cbody%3E%3C%2Fbody%3E%3C!--tracking:ombv10:/library/home--%3E".

EXPECTED
I should be able to purchase games on Steam.