Lately, for some shipment requests, the process status is FAILURE: Unknown error. When a shipment request is redone at a later time, the request will be processed properly in most cases. If this is not the case, the only option unfortunately is to confirm the shipment via the Seller Dashboard.
The IT team is working hard to resolve the issue and to provide a clear error message if an order cannot be confirmed. We apologize for the inconvenience.
Since 02-10 this issue is resolved.