To ensure a smooth build, archiving and then push to AppStore, check the following settings.
***** Especially since Apple started demanding that the dev build for its 64-bit ( and 32-bit ) devices.
I'll add more details as I go.
Before making build, while in Unity:
1. Go to Player Settings > Other Settings > Configuration > Scripting Backend, change value to IL2CPP.
Before making Archive, while in Xcode:
1. Go to Build Settings > Architectures, change value ( from probably "arm7" ) to "Standard architectures ( arm7, arm64 )..."
2. Go to General > Deployment Info > Requires full screen, change value to true ( check the box ).