This problem raises when I connect through proxy internet connection setting in IE. This is not fixed my Microsoft many year now. Online activation, Web Installer, etc will not work when we connect via proxy internet connection.
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Microsoft Web Platform Installer
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Unable to download the product list from . Check your network connection and try again. If the problem persists, report the issue on the Web Platform Installer 4.0 forum at: http://go.microsoft.com/fwlink/?LinkId=145244.
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OK
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Hope Microsoft solves this soon.