eBay Error 21920061: Invalid variation specific Parameters: [variation option label] is not allowed as a variation specific.

Why this happens

One of the variation specific names (such as color, size, etc.) is also a required Item Specific for the main listing. Why eBay enforces this: An attribute that is a required item specific for the category cannot also be a variation name, because the listing would have two conflicting values. When it usually happens: It usually appears in categories that require Color or Features as a main item specific.

How to fix it

This error in other languages

German: Ungültige Variantenmerkmal-Parameter: „…“ ist als Variantenmerkmal nicht zulässig. French: Paramètres de caractéristique de variante non valides : « … » n'est pas autorisé comme caractéristique de variante. Italian: Parametri delle specifiche delle varianti non validi: "…" non è consentito come specifica delle varianti. Spanish: Parámetros de característica de variante no válidos: "…" no está permitido como característica de variante.