Symptoms
In Microsoft Skype for Business Server 2019, when you run the bootstrapper.exe at the location \Program Files\Skype For Business 2019\Deployment, you receive the following error message:
Error encountered: Command execution failed: The given key was not present in the dictionary.
Resolution
To fix this issue, install the December 2019 cumulative update 7.0.2046.151 for Skype for Business Server 2019, Core Components.