Solved! I had confused too. I didn't see Sandbox user in Settings > App Store. Then I read documentation :-) In iOS and iPadOS, the sandbox account appears in Settings > App Store after the first time you use the device to attempt a purchase in a development-signed app. There’s no need to sign out of the non-Sandbox Apple ID. Sign in using a Sandbox Apple ID.

I had same issue with definition: "There are still screenshot uploads in progress". Resolved via AppStore Connect API. Solution is here: stackoverflow

Resolved by uploading a new build via Xcode (build version == AppStoreConnect version)

Workaround: in Xcode, create an Archive, then click "Distribute App". During the upload, the App will be created with your bundle ID.