There are some certificate issues that occur when attempting to use Visual Studio 2019 with GitHub.com when inside the VA network.
      
  
  How to Make Visual Studio 2019 work with GitHub
- Open Visual Studio
- Navigate to Tools -> Options
  
- Navigate to Source Control and set the Source Control Plugin to Git
   
- Navigate to the Team Explorer Window and click the Home button
  
- Open the Settings menu and click Global Settings
  
- Set the Cryptographic network provider to “Secure Channel”
  
- Open File Explorer and navigate to:
 C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Git\mingw32\bin
  
- In the whitespace, “Shift + Right Click” and select Open PowerShell Window here
  
- Run the following command to verify the settings of http.sslbackend=schannel
 .\git config --global --list
  
- Run the following command to set http.schannelCheckRevoke to false
 .\git config --global http.schannelCheckRevoke false
  
- Run the following command to verify the settings of http.schannelCheckRevoke=false
 .\git config --global --list
  
 
       GitHub Handbook
 GitHub Handbook