"__" % of the products in your file did not process successfully. We recommend using Check My File to help you identify and correct common listing errors before updating your inventory

Amazon API returns the error when some required settings/details are missing or invalid in your Amazon Seller Central.

Please check the product logs by clicking the Log icon in the Status column of Listing grid. It helps to clarify which data/settings should be edited. Once you fix the related issues, this error will no longer arise.