I am facing the issue too. Tried uploading 3 different builds, no errors shown in Organizer. Saw the big green tick and success message. In TestFlight it shows up for a while showing only the build number and then it disappears.
No emails so far on issues too. Is there somewhere in the App Store Connect that we can check for logs or anything?
I am using Xcode 13.1 on macOS Big Sur 11.6.1