Is there a way to get the UPC of an active listing from its Item ID (also called Item number) ? I have tried out various calls like findItemsByProduct in the Finding API, findItemsAdvanced, findItemsByKeywords, GetSingleItem, GetMultipleItems, but have had no success with any of them. The ItemSpecifics container in the response returns everything except the UPC. Neither is it seen in the container. Is Ebay deliberately blocking requests for UPC ? if not, I request anyone knowledgeable about this to suggest me a suitable solution for this problem. Thanking you.
That would be every call that starts with "find". Your problem is that the item you are requesting doesn't have a productId. eBay's catalog is not complete. The field is only returned for items in the catalog. Try a more common item like a DVD.