Hi,
Did the issue also happen between normal SFB client (not Lync\SFB SDK client) or just happen with SFB SDK client?
If the issue also happen with normal SFB clients, then please double check if there is any conference policy to block it.
If the issue just happen with SFB SDK clients, then as I know, SFB SDK client in UI suppression could restrict the feature. Please double check the SFB SDK configuration.
As the issue also related with SFB SDK client, you can also post a case on MSDN forum and there are more SFB developing experts will help to solve it. Thanks for your understanding.
https://social.msdn.microsoft.com/Forums/en-US/home?category=SfB
Best Regards
Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.
Eason Huang
TechNet Community Support
