Black Screen during the Live class meeting

[manita]

We have purchased Zoom for more than 1000 member live class meeting, most of my students are having issue like black screen during the meeting, We have tried multiple ways to solve the issue but the problem seems to be reaccuring. Can anyone help?

[zoomer_tom]

Have required firewall ports been verified as open?

Is the presenter trying to play a video when the black screen occurs for the attendees?