Customers recently been receivin error message for American Express transactions

-- url of the page with the problem -- : www.onychair.com
-- HikaShop version -- : HikaShop 3.1.1
-- Joomla version -- : Joomla! 3.6.2 Stable
-- PHP version -- : 5.3.29
-- Browser(s) name and version -- : Mozilla/5.0 (Windows NT 10.0; WOW64; rv:54.0) Gecko/20100101 Firefox/54.0
-- Error-message(debug-mod must be tuned on) -- : Transaction Status: Declined (Authorization with the card issuer was successful but the transaction was declined due to both a card code mismatch and an address mismatch with the information on file with the card issuing bank based on the settings in the Merchant Interface.)

Our payment gateway is through Authorize.net, lately we've been receiving phone calls from customers who are trying to pay through American Express, but been getting the following error: Transaction Status: Declined (Authorization with the card issuer was successful but the transaction was declined due to both a card code mismatch and an address mismatch with the information on file with the card issuing bank based on the settings in the Merchant Interface.)

However, we we take the payment over the phone and process directly through our merchant account the transaction is captured.

We recently switched merchant accounts but made no changes on our settings and contacted Authorize.net prior to reaching out to your, but they state are settings look fine and are set to receive payments from American Express card holders.

Do you have any idea why this is happening all of a sudden? And please provide a solution.

I have reached back out to Authorize.net with your response, and they seemed to have found a solution