I am very sorry for your trouble. I have gone into the payment system to find your case and can see that you have been trying three times.The error that I get to see is the same as yours. That your card was declinded, but with the additional information that it was because of an unknown reason (for us) and that you would need to contact your card issuer for more information. The payment hasn’t been declined by us or by our payment system but by your card issuer. Maybe you could ask your bank?
There is also an option to pay by paypal in case you have that or if you have another card then you could try that.
I hope this will help in some way. Just let me know if it doesn’t then we will figure something out.
Best regards, Ewoud