AMTU : Orders marked as shipped on Amazon are being imported into One Stop Order Processing as unshipped
When you are using AMTU to manage the importing of Amazon orders into One Stop Order Processing all orders are imported as unshipped. i.e. the shipped status is not reflected when importing orders.
If you are processing some orders on Amazon OR marking any orders as shipped on Amazon (or other external software) you should mark the orders shipped (locally) in One Stop Order Proceesing. To do this untick the Amazon option in Shipping tab in Options, shown below:
Mark the relevant orders as shipped in One Stop Order Processing. Retick this option.
Any orders marked as shipped in One Stop Order Processing will update the order shipped status in Amazon.