Same issue here.
I have update to XCode 12 yesterday, and today the issue occur.
The uploaded build occurs on App Store Connect's 'Activity' view (with 'processing').
But after few minutes the build is gone and just remain previous build I upload yesterday.
No email received also.
Wait Apple give more information.
YuChaoHsu
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Just test on my iPhone 11 Pro Max with iOS 13.6.1, the same issue still exists.
Have set the allowLocalEndpointReuse as true