Alitalia MilleMiglia - Problem booking through the AZ domestic site

I called Alitalia today to book an itinerary EWR-VCE (via FCO), VCE-FCO, FCO-EWR, and was told 1) it would be cheaper to book two separate flight pairs, and 2) it would be cheaper still to book the FCO-VCE-FCO segments on AZ's Domestic website (https://www.alitalia.com/EN_EN/). This turns out to be true; however, when I get to the payment page, it says it can't accept either my AMEX Plat or VISA. Is there an issue with using US-issued cards on the domestic site, and if so, is there a way around this problem?

Did you try looking for the fare code on http://matrix.itasoftware.com and then asking your amex plat travel concierge to book it for you using the exact same fare code you fount on the matrix website?

I used this method several time with 100percent success.
Usually the fare listed on the matrix website differs from the one fount by amex concierge by 10eur max.

Good luck.

Ciao

Apparently, because a US card was being used on an Italian domestic website, both AMEX and VISA flagged it as potential fraud.