Symptoms
In Microsoft Skype for Business Server 2019 or Skype for Business Server 2015, a Skype for Business on Mac user updates his profile picture, but other users can't see it. After the Mac user signs in to a Skype for Business for Window client, other users can see his latest photo.
Resolution
To fix this issue, install one of the following updates:
For Skype for Business Server 2019, install the December 2019 cumulative update 7.0.2046.151 for Skype for Business Server 2019, Core Components.
For Skype for Business Server 2015, install the July 2019 cumulative update 6.0.9319.559 for Skype for Business Server 2015, Web Components Server.