Our ePDQ runs fine in a full SSL environment ie we bought an SSL certificate for the domain, the problem I found earlier was using a shared SSL certificate in a testing environment.
With shared SSL Zencart calls the ePDQ module with a variable token (zenid) in the URL and it needs to be called with a fixed URL I guess for security.
In your ePDQ technical settings for "Data and origin verification -> URL of the merchant page containing the payment form that will call the page:orderstandard.asp" make sure the URL is correct. Ours is the https domain followed by
/index.php?main_page=checkout_confirmation
If you are running with a shared certificate you will need to purchase a full SSL certificate for your domain unless you can strip the zenid out of the URL before calling ePDQ. I think the general advice is its better to not use shared SSL with Zencart for a live website.
Cheers,
Mick
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