We tried to connect to Workspace using our internal GitHub repository
However when we specify our repository and try connection we receive an error message:
Failed to perform the specified operation. Please make sure you can connect to the server repository.
PowerBuilder cannot connect to our internal  GitHub server. Also it cannot connect to the public github like https://github.com/Appeon/PowerBuilder-UI-Example

All steps are seen in the screenshots 
-Right click on the No Workspace  line in the explorer 
- specify the repository and the Workspace file in the pop up window "Connect to Workspace "
- Click Test Connection
- Getting the message "Failed to perform the specified operation. Please make sure you can connect to the server repository."

Git Bash doesn't have any problem. We created local repositories using these commands
git clone https://rbcgithub.fg.rbc.com/SQ00/slbrat_cur
and
git clone https://github.com/Appeon/PowerBuilder-UI-Example