My app is in internal testing on iTunes Connect, but I cannot promote it to external testing. It tells me that the test information is incomplete.
I have tried all sorts of things, including reading this doc and this doc on Apple and re-entering all the information again. Playing with the language specifier.
This is maddening, because this exact information worked for a previous build.
I checked and unchecked "Sign-in required" and Saved and the warning icon finally went away.