I wasted the better part of a morning trying to make a train reservation on the Trenitalia website only to find my credit card payment was denied. I finally got through to the Trenitalia call center in Italy. I was told there is a known problem with the Trenitalia website rejecting international credit cards so I must purchase tickets when I arrive in Italy. I also called the Italian tourist board in NYC and I was told that Trenitalia has been aware of this wide scale problem for some time -- and unfortunately they have made no progress. Meanwhile, this means losing out on discounts and special fares -- not to mention added inconvenience. Many complaints have been posted here and elsewhere, but there seems to be little anyone can do. Just hoping to save others the trouble.
This is a common problem that has been thoroughly discussed here.
Which trains are you trying to buy tickets for? Unless it is a night train or during a holiday, there really is not much need to have an advance reservation for trains. I guess one exception would be if you have a large group and you all wish to sit together.
If it is just four or fewer of you travelling on regular day routes, wait until you are in Italy to purchase the tickets. It is easy to do, and the automated ticket machines work very well in stations where there are long lineups for the ticket windows. For more information on using the automated machines, take a look at this excellent walkthrough.
Apart from trying with my verifed by visa credit card ..i also tried with my American express. I got a message from trenitalia saying why my card was denied, they will need a proof of identity and my tax code number faxed to them to estabilish identity. Ofcourse i did not send it to them and landed up purchasing reservations through italiaraila (didnt get any promotional fare that was available at trenitalia website)and eurail pass since my travel involved overnight journey from Rome to interlaken and I wanted to be sure that I had my reservation for the couchettes.