I have a pair of sites I manage that are on Magento 2.2.4 and 2.2.5. Both are using Authorize.net Direct Post and I have applied the Authorize.net MD5 patch from Magento to utilize the signature key instead of MD5. Both sites are able to properly process valid cards but failed transactions do not get canceled as expected. This was hit and miss prior to the patch so that might not be related.
I have both sites properly calling the Magento cron on a schedule for every two minutes. Even after the cron has run, the order is not canceled and remains in pending. I have set Direct Post to Authorize & Capture, but that did not have any impact.
The reporting of this transaction to the Merchant has timed out. An e-mail has been sent to the merchant informing them of the error. The following is the result of the attempt to charge your credit card.
This transaction has been declined.
This is what I get as a response from transact.dll. I have Debug enabled for Direct Post so I get logs and I am not receiving a response from Authorize.net. I'm gathering that will be my issue but what would prevent Magento from seeing the response?