I faced the same issue. I tried multiple cards, different computers, and even mobile phones, but got the same error every time. I also checked with the bank, and they confirmed they could not see any transaction attempt, which means the payment request is not even reaching the bank. You may also notice that the error appears immediately after clicking pay.
What worked for me was using a card other than a regular bank credit/debit card, such as a virtual card or a card linked to an investment/payment app. I’m in the UAE, and I successfully used a card associated with O Gold, which is a gold investment app.
You can similarly try with any bank virtual card, or cards/services like Etisalat Wallet, Botim Money, or similar payment apps.