A required attribute for the product's category is empty or missing. The item cannot be ingested or published until the required field is supplied.
Each Walmart product type has a category-specific spec sheet listing required attributes (e.g., Brand, Manufacturer, Color, Size, Material, Gender). Required fields differ by category, so a feed that worked in one category may fail when an item is mapped to a different product type. Empty strings, nulls, and placeholder text all trigger this error.