I have attempted to ship multiple items but continue to get this message. "Amazon cannot provide prep and labeling services for items that do not have a single scannable barcode (GCID, UPC, EAN, JAN, or ISBN) that corresponds to an ASIN in Amazon’s catalog. For more information, go to FBA Label Service." None of the items I have selected seem to have a single scannable barcode. As an alternative, the Unit Labeling defaults to By Seller. How am I supposed to label the products if they're being sent directly to the Amazon warehouse? Any advice will be greatly appreciated.