I've just tried to set up a video conference call using skype for mac. Before the meeting, I skyped in a number of my skype contacts and had a 4-way video call with no problems.
When it came to the real conference, I was not able to combine the different contacts into a single call. I could call one contact, but then the "Add other contacts to this call" option was not available.
The contacts for the actual meeting have skype for business. Is this the issue? Are there compatibility issues that mean skype users cannot conference call skype-for-business users?