I sending API request to Square Checkout API from my WPF applicatin. For Production it responses Success and Opened payment URL in wpf Browser control. But after submitting on Payment via test cards it gives an Error "We are unable to complete your request at this time. Please try again." I am Referring :Quick pay checkout
Check Images Below Test card used for payment
I expect the success result page described at Quick pay checkout
At this time our test cards are only valid in Sandbox. You'll need to use a valid credit card to process payments for the production links you created. 🙂