https://www.theverge.com/2019/1/30/18203551/apple-facebook-blocked-internal-ios-apps

Apple has shut down Facebook’s ability to distribute internal iOS apps, from early releases of the Facebook app to basic tools like a lunch menu. A person familiar with the situation tells The Verge that early versions of Facebook, Instagram, Messenger, and other pre-release “dogfood” (beta) apps have stopped working, as have other employee apps, like one for transportation. Facebook is treating this as a critical problem internally, we’re told, as the affected apps simply don’t launch on employees’ phones anymore.

The shutdown comes in response to news that Facebook has been using Apple’s program for internal app distribution to track teenage customers with a “research” app.