I'm trying to configure the payflowpro add-on module... but when I process the order, I get the following error:

We were not able to process your order. Please select an alternate payment method, or contact the store owner for assistance. (12 )

There were no docs with the add-on, so I'm wondering where to start looking.

The server is running curl, and I have verified that all my login, vendor, etc creds are correct.