CBSubs Subscription cancellation didn't cancel in Authorize

We have a subscription based website with Authorize as our gateway. The unsubscribe button has been working for our users who wish to cancel their subscription. It removes their permission from their site as well as removes their subscription on Authorize.net's side, stopping any future billing.

We recently found a user had cancelled her subscription, we received the email notification, but she was never removed from her subscription/recurring billing in Authorize. Unfortunately we didn't find this till a few months later, so she was billed so many months beyond her cancelling.

This appears to be a unique case since there have been cancellations before and after which worked accordingly.

We are going to contact Authorize as well as our Merchant Processor but we wanted to reach out on here to see if maybe anyone has experienced the same issue, or has any ideas whatsoever.

Any input/help would be greatly appreciated since the client is looking for some type of explanation.

I've never heard of this happening. Maybe Authorize.net connect failed for whatever reason so the cancellation didn't go through? Was there an IPN for the cancellation? I would contact Authorize.net and see if they have an error on their end when the cancellation was made.