Krileon,
On the Authorize.net payment gateway settings, on the Enable Authorize.net, we have "Yes, AIM+ABR: Single payments or Automated Recurring Billing at user's choice for autorecurring plans"
From reading the manual, page 216-217, that is all that I saw that needed to be done. Enlighten me.
On the Authorize.net, Merchant Profile it has:
Automated Recurring Billing (ARB): Enabled
However, further research guided me to update the Authorize.net account with the Silent Post URL and MD5 Hash. I tried again and did not get this error but got a E00022 Error. Seems Authorize.net won't accept recurring of less than 7 days. So I changed my test plan to 7 days, tried again and got a clean authorization.
Thanks for pointing me in the right direction.
Luke