Having this same issue. Created a test session and the test server does not have any of the interactive whiteboard features.
Hope this helps!
Oh, excuse me. I do not know how did i miss your reply.
Anyhow, my screen of white board is not appearing. so, can not access the sidebar to the right for the tools to manipulate the screen.
Brainstorming here... If you click on the plus icon in the bottom right, and select Upload Presentation, do you see a default file in there? That's what provides the default welcome and additional white screens.
Although If I understand clearly you have already figured out that the issue is the processing due a setting in your BBB server. If that is the case, and since it would not be related to the plugin or Moodle, I would recommend you to post your question to the BigBlueButton mailing list (https://groups.google.com/g/bigbluebutton-setup). It may even be a bug that the developers paroling that forum would be able to catch.
But if It may be
Yes, I have posted in bbb group. Had to go through alot of checks but could not resolve it till now. But yes. It is not plugin issue so I will close this.