AMEX/Discover Auth.net not working

[webrob]

Did you test a transaction on AuthorizeNet itself?

The transactions work from the authorize.net virtual terminal in my authorize.net control panel

What happens if you switch to Classic Template to test this?

I do not have the classic template folder anymore

What version Zen Cart are you running?

1.3.7

Clean install or an upgrade?

Clean Install

How did you install it? How did you upgrade it?

This is the original authorize.net payment module that came with Zen Cart...I think!