No sound no video android app on terminal visio

Hello,
I try to use the Jitsi Meet Android app on a Visio terminal under Android 7.0.

I tried several versions of the app (whose last) but I always have the same problem:
I enter the conference, and no sound and when I activate the camera I return (for few seconds) but nothing for correspondents.

With firefox by walking against everything.

Do you have an idea of the problem?
It bothers me to use firefox because given server configuration I have to used the “computer” mode and not moving because refused by the server. Even if it works well, the display is not at all suitable.

thank you