i had the same issue i deleted (mark expired) all the versions of app testing version in App TestFlight section and done the trick for me ;) attach is the screen shot of activity.
When you delete all test information from TestFlight, make sure you delete it for every language.
In the testinformation page, select every localised language and check if the form is empty.
First, You must remove all build and user from TestFlight of that app. After its looks like below.
If you still not match last criteria than Sign Out and login again.
Do the same step as @Imran Iqbal answer, if your app is Sign-in Required, uncheck Sign-in Required also, like:
then, you can transfer app.
i had the same issue i deleted (mark expired) all the versions of app testing version in App TestFlight section and done the trick for me ;) attach is the screen shot of activity.
I've search for a long time and to me this worked:
To me this works. Hope help someone.
Another possible reason:
When you delete all test information from TestFlight, make sure you delete it for every language. In the testinformation page, select every localised language and check if the form is empty.
For me it was localised test descriptions. Make sure you check that drop down list on the right and clear out info for all languages.