eBay Error 21916605: Only single item quantity is permitted when the listing is in auction-style or under selected categories in Fixed Price format.

Why this happens

The Quantity is greater than one, but the listing is either an Auction, or in a special eBay category that only allows one quantity per listing. Why eBay enforces this: Auctions sell one item at a time, and some categories allow only one unit per listing. eBay refuses a higher quantity in those cases. When it usually happens: It usually appears when an auction template is used for multi-quantity products.

How to fix it

This error in other languages

German: Bei Auktionen und in bestimmten Kategorien im Festpreisformat ist nur eine Stückzahl von eins zulässig. French: Seule une quantité d'un objet est autorisée pour les annonces au format Enchères ou dans certaines catégories au format Prix fixe. Italian: È consentita solo la quantità di un oggetto per le inserzioni in formato Asta online o in determinate categorie nel formato Compralo Subito. Spanish: Solo se permite una cantidad de un artículo en anuncios de subasta o en determinadas categorías en formato de precio fijo.