NodeXL Pro payment error

Mar 18 at 3:53 AM

I tried to purchase NodeXL Pro (Academic & non-profit users) a few times but keep getting the same error. It says ‘The card you entered cannot be used for this payment. Please enter a different debit or credit card number.’ My colleague and I have both tried purchasing it using our respective cards (Mastercard for both) and both of us receive the same error. Any idea what the problem might be? We don't have any issues making purchases on other websites and only encounter this error when trying to make payment for NodeXL Pro. We would need to use NodeXL Pro in the coming week and would like to pay for the license as soon as possible so that our work will not be delayed. Please let me know what can be done.