When you upload the archive to the App Store using the tool from Xcode, you may get the following error:
Reason: Your Icon image has feature: Alpha
Solution: Make a PNG without an alpha channel.
How to fix it:
Open file: Assets.xcassets From Runner > Runner
1. Select the AppIcon item, scroll down to the bottom to select the image size 1024 pt.
2.Right-click : Open in Finder
3. Double Click on that photo to open
4. Select File > Export...
5. In the Export screen: Untick Alpha, save the image file
6. Replace the entire App icon with that
7. Archive and Distribute => OK