Hi @Hamed Vaziri ,
Welcome to Microsoft Q&A forum.
The error message does say that the issue is caused by authorization. If this issue is not a potential issue, then you may need to check the authorization. I would suggest clean web browsers’ cache, remove Credential Manager and reset it then restart your machine(I know you have done this, but maybe try to restart machine?), check if you are using any proxy/antivirus/application which may block something, and try to install the latest VS 2015 Update package.
And if it is possible, I think you can try to test this on another machine with VS 2015, and if the same issue appears, I recommend directly reporting this issue on GitHub, or adding comments in the thread that you shared.
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