According to a report from MacRumors, it seems that several users have created a thread on the forums about how they are still unable to add more users to a FaceTime call. When trying to do so, they are finding that the “Add Person’ button remains greyed out. This means that if you’re trying to start a Group FaceTime call, you will need to start the call with all participants in the call, as opposed to being able to add them in at a later date.
Apple had previously disabled Group FaceTime while they worked out the privacy bug, but it seems that despite the bug having been fixed, Group FaceTime still has not been fully restored to its previous state. Apple claims to be aware of the issue and that they are unsure when it will be fixed. In any case, as we said, the workaround is that you’ll need to ensure that all the people you want to have in the call are added into the call at the start, but hopefully a fix will be released soon all the same.