Sounds an odd problem - error "unknown order/1/r" is listed only as a mismatch between the calling URL and what you have configured in your ePDQ tech settings. If your SSL domain looks like https://<your_domain> then its not shared. The "zenid" token can show up in the URL for various reasons, search in the forum for more info.

I found it useful to see exactly what was being called and the parameters being passed - in a Chrome browser run through an order checkout, at step 2 of 3 right click the "Continue Checkout" button and choose "Inspect element". The "action" setting on the form named "checkout_payment" should match your "Data and origin verification -> URL of the merchant page containing the payment form that will call the page:orderstandard.asp" setting.

If you do "Inspect element" on the "Confirm the order" button at step 3 of 3 you see the call to ePDQ and the parameters being passed.

Support was helpful but quite slow, I hope they can sort it for you.
Cheers,
Mick