Credit Card Error in Magento 2.2 - An error occured on the server.

[jlucano]

I've found several topics on this for v 2.1 but nothing on 2.2 that I can see (please let me know if there's already a solution that I missed). I'm new to Magento so it may just be me not understanding but I can NOT figure out how to fix this. So I try to place an order with a credit card. The generic error shows up saying "an error occurred on the server." However, my card still gets charged AND the order appears on the admin side but no order receipt email to the customer and no redirect to the success page.

 The URL is foam-tapes.com. Paypal works so at least there's that. I'm supposed to officially "launch" the site next week but obviously can't do that if our customers can't pay us. Any help would be appreciated. Thanks!

[Kollltd]

Were you able to get this fixed? We're experiencing the same issues with Magento 2.2. 

[Sheba]

Hello.  I have the EXACT problem.  Please share how you resolved it.  Thanks.

[Sheba]

Found the issue in the exception.log: The transaction was declined because the response hash validation failed. Entered the same MD5 Hash in Authorize.net into Sales > Payment Methods > Authorize.net > Merchant MD5 and problem solved :=)