Second guest cannot view cameraand desktiop sharing!

Hi. After installing Jitsi and activating the authentication in it, the first user who joins the conference can see the teacher’s desktop and the webcam images, but as soon as the second user joined to jitsi, the webcam image and shearing desktop It will be disconnected and all subsequent users will have the same problem. Finally, if all the guests are disconnect and only the admin and a guest user remain, the camera and desktop shearing image will be activated again for that one guest!
Please Help me.