This is a continuation of the message:
I could not post another message in the former topic (the message woupld post but then disappear), so I am starting another thread here.
Just want to make sure it not your account that is having issue, not returning any response. It look like you posting the data to the /datavalidation/ page. What we need change the relay response url to https://developer.authorize.net/tools/paramdump/index.php to see if it might be an account issue that it not post any data.
Does the code still work in the sandbox with the test account?
If I try to use https://developer.authorize.net/tools/paramdump/index.php for the callback url, the system will not even navigate to the payment page, but will return "url not found" error message. The code fails in the same way on the main site in both production and test modes. I am getting other errors when I try it from the sandbox account, but that may be because my sandbox account is old/expired.
Bottom line - when we need is for Authorize.net to optionally save a log of the callback messages it sends.