When multiple users are internal behind NAT, it seems that you can't share voice, video, screen, etc, between them. External users can see presenter fine.
That's a very broad question. What specifically are you asking? Conferences work fine, but media (audio, video, screen share) does not work between internal users. External users get all media. I use same url inside and out with split dns. System is configured with correct internal and external ip addresses. Firewall checker is all good. I think I have all correct port forwards. Are there any additional new ports beyond the published list? I have the extra ports 9250-9500.
I just had a WebMeeting like that a little while ago and technically speaking there should be no problem. As there can be many reasons for this, I would recommend contacting the Support Team by opening a ticket about this.