I recently created a new app record in AppStoreConnect. The app is still in development and testing, so we use this for TestFlight builds. The app has a complete app icon internally, and shows up in the Simulator and devices correctly.
But in AppStoreConnect, it shows the generic app icon placeholder.
I contacted Apple support about this, and they told me I needed to include the app icon in the app. I told them I already do, and showed them the screenshots. They basically said sorry, not my problem, try the dev forums.
So here I am.