Symptoms
In a Microsoft Skype for Business Server 2015 environment, a user can’t create a Skype meeting on behalf of another user by using the Skype for Business on Mac client. When the user schedules the Skype meeting, no information is presented and all is blank. This issue occurs when the two users are homed in different pools.
Resolution
To fix this issue, install the July 2019 cumulative update 6.0.9319.559 for Skype for Business Server 2015 and Unified Communications Managed API 5.0 Runtime.
Workaround
To work around this issue, you can use Outlook on the web (formerly known as Outlook Web App) or Skype for Business on Windows client instead.