Global Trade Item Number is absent or fails Walmart's GS1 validation. Item won't ingest until a valid GTIN/UPC is supplied.
Walmart Seller Center uses identifiers (GTIN, MPN, brand, SKU) to match catalog records. Issues come from invalid format (non-numeric in a GTIN field), brand-GTIN mismatches in GS1's database, duplicate IDs across SKUs, or missing required identifiers for the category.