If you see items showing up with this error message in your Stranded Inventory on Seller Central and you're using Seller Engine Plus to create FBA shipments it most likely means that they are in a shipment but you never created FBA listings for them. To fix this issue upload the items from shipments after they are set to 'Shipped' so that the needed listings are created on Amazon.
Also, Amazon will de-list an item right away if there isn't a price attached to it, or if the price is too high or too low. Sometimes the upload files are mostly accepted excluding a few items for pricing issues.
Other causes of stranded inventory are things like:
• Forgetting to upload the listings
• Items put into the wrong shipment (unexpected items in shipment)
• Missing items (they did not arrive)
• Item(s) was uploaded with no price
To create listings open the shipments that contain the items in stranded inventory. If you don't know what shipments they are in you can find out using the 'Shipments of SKU' field, for instructions click here.
Once you find the shipments that contain the problem items select all items in it and click 'Upload' > 'Add new items [...]'.
NOTE: If the items still show up in Stranded Inventory check the processing report provided in Seller Central under Inventory > Add Products via Upload.