Hello,
We are aware of this regression with the latest Flash Player (15.0.0.152) on Mac and Flash Player team is working to fix this issue. But, this issue should not occur in Adobe Connect add-in(11.9.971.247). Are you able to launch the addin from your mac or is the meeting opening in browser (flash player)? Also, Can you try some other browser to launch your meeting?
Thanks
Sameer Puri