In the way it is right now, the preuploaded presentation is uploaded and hosted in Moodle. When the meeting is created in BBB, the plugin passes as part of the Create request a URL that can only be used once. BBB then pulls the PDF and process it to show it in the live session.

If the Moodle server is behind a firewall and does not allow inbound traffic, the presentation can not be pulled (therefore processsed) by BBB. This makes the presentation area to show as if it had failed.

The only way to overcome this would be to pass the full file as part of the payload during though a Create POST request.

For this and because the PFD (or other files) can be bug enough it would be neededed to process create as a multipart request .