I have made an app available to external TestFlight users. They have received the email and installed the app as expected. They have version 1.0, Build 1.
However, I have now uploaded a new build (Version 1.0, Build 2).
This has received approval. In the External Testing page, I have added and selected the new version. This new build now says 'Testing'.
However, the users of the previous build have not received any notification and in the TestFlight app it still says Build 1.
Does anyone know how I can make the current users get the new build? I assumed this would be automatic and I can't find any info on this situation.
This doesn't seem to be working today; it seems to be a bug in Apple's side where the selection of the new version in TestFlight isn't correctly propagating out to the other systems. You'll find people on twitter and Apple's developer forums complaining of the same issue. It affects internal testers too.
I think we just have to wait for Apple to fix it; presumably that will happen in the next 24 hours...