12 December 2014
As several people have noted in the forums, trying to use TestFlightApp with the iTunes Connect portal isn't working quite like it should. After some research, it seems that including the entitlements in the provisioning profile isn't enough to satisfy some of Apple's requirements. An extra entitlements file needs to be added to the app bundle that is the same as the entitlements.plist file that is created by Xcode when adding other entitlements.
While we work to resolve this, you can still use TestFlight successfully in the mean time. You just need to use a 3rd party product called AirSign.
After downloading/installing...