The deactivation of Group Facetime has since been reflected on Apple’s system status website. Over there, FaceTime is shown to have an ongoing issue since 11:16 AM Malaysian time with a specific notice that said Group FaceTime has been temporarily suspended.
In terms of customers experience, there are no changes to FaceTime UI itself at the moment. Users can still see and have the option to add another number to their FaceTime call although they will not able to actually include the additional number to the call. Apple has stated earlier today that the company is already working on a fix to address the issue and is expected to be deployed later this week. So, stay tuned. (Source: Apple)