Group FaceTime Bug Fix Included in iOS 12.2 Beta 3
Apple addressed the Group FaceTime bug in the iOS 12.1.4 update released on February 7, but there has been no new iOS 12.2 beta until today, so the Group FaceTime feature has remained unavailable to iOS 12.2 users because the server has been offline.
The FaceTime bug allowed someone to spy on you without your permission or knowledge. By exploiting the bug, a person could initiate a Group FaceTime call with you and then add themselves to the call again to force a Group FaceTime connection, as demoed in the video below.
When the Group FaceTime connection was forced using this method, the bug caused the person to be able to hear the audio on your end, even if you did not answer the call. In fact, on your end, it would continue to look like the standard incoming FaceTime call interface. In some situations, if you pressed the side button to silence a call, it would even give the person access to your video.
Given the severity of the bug, Apple took its Group FaceTime server offline while preparing the iOS 12.1.4 update. Group FaceTime was reinstated on devices running iOS 12.1.4, but it does not work on iOS 12.2 beta 2 or devices with iOS 12.1.3 or earlier installed.
It should be noted that Group FaceTime is still somewhat broken following the update. In iOS 12.1.4, there is no option to add a person to a one on one Group FaceTime call because the "Add Person" button is grayed out. Group FaceTime calls need to be started with two or more people at the current time.
Other users have been unable to use Group FaceTime at all, and have had trouble adding additional people even during a call with more than one person. Apple is presumably working out these bugs and will have further fixes available in the future.