When using the Acctivate webstore module for importing and exporting BigCommerce order information, users may receive the following error in the Shipment Export section of the webstore synchronization.
Status returned from web server: 400 / Message: The required field ‘items’ was not supplied. (Subdocument ‘shipment’)
The BigCommerce V2 webservice API will request the quantity shipped for each line item for the Order Shipment. In the webstore template options, there is an option regarding which quantity should be exported for the quantity shipped. By default, the invoiced quantity is selected for the line items of the shipment. In some cases, however, shipments for orders that have not been invoiced will not have an invoiced quantity. This means, these items will be excluded in the shipment order API request.
A simple solution would be to modify the default ship qty value from “Invoiced” to either “Ordered” or “Scheduled”
Once you have modified the BigCommerce V2 template option, simply try the export, again. Shipments for your web orders should be successfully exported at that time.