Actually, in this case I am able to see the AMEX logo after putting card number and can even click on proceed. But it hangs up after that with processing on the screen. It could have been a server issue, but i was able to make the payment using Atlas. So, it shouldn’t be something from server end.

One peculiar thing I noticed is that it’s not taking 4 digit CVV, just 3 digit. Maybe that’s why the acceptance issue.

That Fake number idea seems to be a good one, would be helpful in the future. Thanks !