Glitch Preventing Order Cancellation

I have an order where the customer requested cancellation for the reason "Item Sold by Third Party". I don't know if this reason is causing the issue or not, most cancellations leave the reason unspecified.

The problem is that when I click "Cancel order" in the Action column, it brings me to an order page with two notifications, the page footer, and no other content. The first notification in red says "There was an error, please try again later.". It has been 6 hours since I first tried this and Amazon is not fixing it. The second notification in blue says "We would love your feedback. Click here to let us know how we’re doing.". I have used the latter to report my dissatisfaction. For what it's worth, clicking the order number instead of the "Cancel order" button brings me to exactly the same page. I can print a packing slip from the Manage Orders page, but I have no reason to. It's the only thing Amazon will let me do with this one order.

How do I prevent this order from going into late shipment? Is there any other way to confirm a cancellation to get around this?