visual studio for mac cannot create workspace

Question

I try to manage workspaces in Visual Studio for mac with TFS extension. I don't have any workspace so I click on ManageWorkspaces in SourceControl Explorer. Then I click on add button in order to create a new workspace. It works great until here. I enter workspace name, then I select a working folder. And After I click on OK button, it gives the error that says:

Cannot create the workspace.

value cannot be null.

Parameter name: Computer.

It doesn't go through and create a workspace. I follow the directions in Microsoft link https://docs.microsoft.com/en-us/visualstudio/mac/tf-version-control. But it gives the error above in the manage workspaces section / 6.step

Need help. Regards