Symptoms
When you try to run Skype for Business App, the app won't start. However, you can run Skype for Business Web App.
Cause
This issue occurs because the default value of the MeetingUxUseCdn value is set to False.
Workaround
To work around this issue, set the default value of MeetingUxUseCdn to True.
Resolution
To fix this issue, install the following update for Microsoft Skype for Business Server 2019: