I managed to have a dig into this - one thing I noted in the logs for the F/order ID on your store, is that the it transitions to a closed state at 14/11/2021 22:42:17 (UTC) when an Auto job for Order Fulfillment runs. The f/order that belongs on the order IID transitioned to a closed state at that timestamp.
I checked out the checkout settings of the store, and the toggle to 'Auto fulfill an order's line items after an order is paid' is set to checked. That auto fulfill job I mention, won't run unless the toggle is switched on - which looks to be why you're getting the receipt of the message about it not being in an open state. Is it part of your workflow to have it set to Auto fulfill? Thanks!
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