"Automated Recurring Billing is not enabled." error for Membership Plugin

I am currently running into an issue with the Membership plugin. It is currently activated on a site using the primary Authorize.net payment gateway (not AIM or ARB).

When my Authorize.net account is in "Test Mode", the plugin works properly. Upon entering test credit card credentials, Autorize.net processes the payment, sends the automated email, and logs the event.

When I switch Authorize.net from "Test Mode" to "Live Mode" (with no changes to the Membership plugin settings), I encounter an "Automated Recurring Billing is not enabled." error at checkout.

All of my Subscription Plans are set to "Finite", so I don't know why I am getting this error - nor do I even have the need for recurring billing.

Please let me know what I need to do to remove this error and allow the plugin to process the payment.

Thanks in advance for your help.