Apple has currently disabled the ability to make group calls in FaceTime. The reason is a serious security vulnerability.
The problem is that you can establish a connection with audio and video streams to the called iPhone without the owner even accepting the incoming call. Moreover, it is not possible to detect that the connection is established.
The trick is quite simple: you call the desired subscriber and then add another subscriber: yourself a second time. This immediately establishes the audio connection even though the called party has not yet decided to accept the call. If the called party presses the side button, the video connection will even be established.
Since all this is not very helpful for your privacy, Apple has switched off Group FaceTime directly until the problem is solved, so you don’t have to switch off FaceTime in the iPhone anymore.
