It seems someone has forgotten to turn on iTC access for Xcode 9 beta 5 -- or there is some major bug with this release. (Since access was fine in beta 4)
Since Monday whenever I hit "Upload to App Store" in order to update the Testflight of an iOS 11 release I get a "No accounts with iTunes Connect access have been found for [...]" and it lists my correct Apple ID (which works fine in Xcode 8.3.x incidentally).
Sometimes this behaviour varies. Yesterday for a while it would connect and upload data, only to get a message that the Xcode toolchain was wrong and I could not upload submissions using it. This is also the behaviour I get from Application Loader.
I know someties it takes a little while for iTC to catch up with a latest beta release, but it's been days now, when can we expect this to start working?