Here’s a quick one that I hope helps someone in a bit of a bind.
As you may or may not know Skype4B Broadcast meetings are hosted on the Azure media services pool part of Office365, as part of that your client needs to be able to connect to the Office365 AVMCU.
In some cases when you attempt to join a broadcast meeting as a presenter, the “Start Broadcast” button never appears and you are stuck with a “Connecting…” message despite you being able to see others hosted on the meeting.
This can be because the login dialog for your Office365 session gets hidden under the meeting window as a few popups appear at the same time.
Enter the username and password and hit OK. In some cases you may have to rejoin the broadcast to resolve the issue.
I hope this helps someone else, as I was buried in snooper logs and blaming firewalls for this.