I was submitting an app to the iOS App Store a few days ago, and got this message from Xcode. Before I had time to resubmit it, Apple has already started reviewing my app. Is this something I need to worry about?
Edit: The app was accepted a few days later.
I had the same problem and Google led me here. From my understanding a checksum is used to ensure that the file Apple received is identical to the file you (thought you) uploaded to them.
I decided to delete my upload and try again. This worked and I didn't get the error message again. Here's what I actually did:
In iTunes Connect:
In xcode: