I just upgraded my store from v7.1 to v9.0 and it seems that the upgrade changed something with credit card processing as I can't complete a test order. We're using Authorize.Net for our payment gateway and the card processing was working fine before the upgrade. Upon clicking the "Place Order" button on the order confirmation page now though, I'm redirected back to the "Payment Info" page with an error that says "The cardholder authentication value is invalid."
I followed the v9.0 upgrade guide to a T and didn't change any of the AppConfig values related to the payment gateway. Any ideas how I can fix this?