Sometimes Seller Central will not correctly read that your box content is going to be provided through their MWS using InventoryLab. When this happens, we have a quick way to correct this issue by refreshing the box content setting for working shipments.
1. From the List>List & Prep page, locate the shipment under Working Shipments and click the 3 horizontal lines next to the shipment you need to refresh.
2. Click the 'Refresh Box Option' selection.
3. Refresh the shipment page in Seller Central. If if as not updated, you may need to resend your box content feeds.
That's it! Your shipment in Seller Central should appear as it should for you to move on with your shipment.