TestFlight doesn't send in-app notifications.

I have no problem receiving notifications from any other app, but anytime an app I'm beta testing releases an update, I don't get an in-app notification from TestFlight. I only receive the emails (which I would like to disable). I've tried deleting and redownloading the app and signing out and back into iTunes in the iOS settings, but neither have fixed the issue.

Anyone else experienced this or have any hindsight on how to possibly resolve the problem?