There is some problem in phone video calling

Only to the administrators and owner of the server is getting this problem. While owners try to get in the voice chatting room with a camera on, it works. However, after entering in voice chat room owner of the channel cannot transfer from voice chat to video chat. This case is only valid to owner of the channel. All the interface and administrative authority. But the problem have not been solved. So if you guys can solve this problem, could you fix this problem as fast as possible? I will optimiscally anticipate you guys' effort in this problem solving! Thank you