“There was a problem with your submission: 3d secure authentication is required for your payment”
The message shows up before(!) the 3ds secure layer shows up. As this layer needs some seconds to load, customers are irritated and stop the payment process. That happened several times and customers complained.
There should be NO error message, before the credit card payment process has been finished.
This topic has been described already by someone else, but the Gravity forms support staff completely misunderstood the issue (They thought it is payment related buying gravity forms; This is not the case. It is stripe plugin related).