I tried both Visa and Mastercard credit cards, and my bank debit card (all US), and all were declined.
Then with one of my credit cards, Capital One, I created a virtual card through their web portal. That worked like a charm in terms of setting up my SmartEX account so I could buy tickets (more than a month out, so didn’t attempt to make the actual purchase just yet).
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by sjedinjenoStanje