When I ran into this issue, my first thought was to search Stack Overflow for solution. I did the search, found several topics. But, unlike my issue, those posters got
I've had the same issue and have found out that my Provisioning Profile for Distribution "somehow" disappeared from the Apple Developer Portal. But when I tried to re-create it, I received error message about the existing one (which I couldn't find at all).
Finally, I've just created a brand new Distribution Provisioning Profile, downloaded and installed it. In the end, I was able to validate the application package and upload was successful.