Hi jminer,

We could help you resolve the issue in private support ticket.

To summarized:
when you have issues with payment processors, always check 3 areas:
1) CBSubs notifications, including detailed view and RAW results.
2) CBSubs History Logs -> filter for error logs type
3) at gateway, in their notifications history

In your case it was:
IPN notification not authenticating at payment gateway

And by looking nearer:
2Checkout: INS Fraud detected: invoice_list_amount: 15.75 not corresponding to basket total expressed in gateway currency: 5.25

You then saw that There was a price error with the 2CO plan.

So case is solved.
I wrote the above so others having any issue can see how to find the reason.