“Missing GTIN” in Merchant Center: what to enter, where

What Google's message means

The product has no gtin (the barcode: EAN, UPC, ISBN) in the feed. Google uses the GTIN to match your offer to its product catalogue.

Not disapproved, but without a GTIN the product cannot join Google's product-comparison groups, gets fewer placements and no product-rating or specification enrichment — Google calls it 'limited performance'. For brands that require a GTIN it becomes a disapproval.

The fix in Shopify

1. Products → the product → each variant → Barcode (ISBN, UPC, GTIN, etc.): enter the full barcode digits — EAN-13 in India and Europe, UPC-12 in the US, ISBN-13 for books. Save.
2. No barcode at all (handmade, custom, vintage): Products → select them → Bulk edit → Columns → add ‘Google: Custom product’ → set it to TRUE; the app then sends identifier_exists: no. Fill Vendor as the brand. Save.
3. Google re-checks the product at its next crawl (usually within a day); the next RevenueCue scan confirms it's clear.

The fix in WooCommerce

1. Products → the product → Product data → Inventory → ‘GTIN, UPC, EAN, or ISBN’ (WooCommerce 9.2+; on variable products, each variation's own field): enter the full barcode digits. Update.
2. No barcode at all (handmade, custom, vintage): leave the GTIN field empty and fill Brand and MPN on the Google for WooCommerce tab, so Google gets brand + MPN instead.
3. Google re-checks the product at its next crawl (usually within a day); the next RevenueCue scan confirms it's clear.

What it costs while it's down

Products flagged this way still serve, but Google shows them less than competitors with complete data. Their listed price is what's being shown less often; a free scan names each product and adds up the listed value at stake.