Using Authorize.net with Marketpress

Hi,

I'm using Authorize.net on Marketpress. I have setup the Login ID, Transaction ID, and MD5 Hash (I've done this previously with another cart without issue). On checkout I get the following error:

"Oops! An error occurred while processing your payment.
There was a problem finalizing your purchase. Please go back and try again."

I am wondering how to debug this issue so that I can resolve it.

I have assigned login permissions to the https://mychiroblog.com multisite. The cart is active on https://chirodesigngroup.mychiroblog.com

I setup a $1 test transaction here:

https://chirodesigngroup.mychiroblog.com/store/products/test-product/

I used a valid credit card when I received the error.

I looked in the backend to see if there is any error log for the cart but I couldn't find anything.

Thanks,
Pat