License question when seller on marketplace says no

Understand the info above but how do I get Epic games to make final decision regarding a dispute with one of your sellers who agreed to your EULA and now tells us we cannot use their icons for our app?

Our app has literally 100’s of different custom textures, icons, add ons , images , custom blueprints and this specific sellers icons are only a component/subset of the bigger solution? Our app can exist without their icons but we’re trying to expand our overall app icon set and frustrated a seller is trying to block usage.

Isn’t that the whole point of marketplace? Use various content, plugins etc with enteral engine to create a custom app or game?

Appreciate your help and guidance .