Fix “Item missing required attribute” on Google Merchant Center

This is the parent issue that branches into specific attribute requirements. The actual missing attribute depends on the product's category. Google's documentation lists requirements per Google Product Category — apparel needs gender, color, size, age_group; food needs ingredients; electronics needs energy_efficiency_class for EU markets; restricted categories have category-specific requirements.

The triage approach: don't assume which attribute is missing. Open the item in Merchant Center and read the specific issue detail; the parent flag in Needs attention surfaces, but the per-item view shows which specific attribute triggered it. Often the missing attribute is something you didn't realise was required for the specific category.

The cross-category trap is what catches multi-category catalogs. Apparel items require gender; if your feed pipeline doesn't populate gender for everything (including non-apparel items where it's optional), an apparel item without gender flags as missing required attribute. The fix isn't to populate gender on toys and electronics — it's to ensure gender is populated on every apparel item specifically.

For attributes that vary in requirement by sub-category, the deep-mapping discipline pays off. Energy efficiency class is required for EU appliances but not apparel; populate per Google Product Category, not universally. Bulk-filling required fields across categories where they don't apply creates noise that suppresses listing quality scores.