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The error is: paypalpro Paypal IPN fraud attempt. ERROR: paypal subscription IPN type subscr_cancel for a basket without auto-recurring items: Invalid transaction. Please contact site administrator to check error log.

That sounds like a cancellation IPN was received for a basket that doesn't have recurring payments so there's nothing for PayPal to cancel. You'd need to PM backend super administrator login credentials for me to review the IPN history as I've no idea why it'd be doing that.

Oddly, we have the normal Paypal Gateway also setup and it reports back fine. It's just the Paypal Pro gateway that won't report back. In looking closer this morning, I see the normal Paypal has a field for 'Your Paypal Identity token' but the Paypal Pro account does not. Is there a reason one Paypal Gateway has it and the other does not? That's the biggest difference between the two that I can see.

You're using "Website Payments Pro" which is their older API. Their replacement for it is "PayPal Payments Pro" which uses their "Payflow" API. The gateway supports both. Trying to use PayPal Standard and Website Payments Pro at the same time may conflict with one another since they share a lot of parameters.