Visual Studio/Web Essentials Won't install

I just got this error message when trying to install WebEssentials into VS 2013 Ultimate:

09/02/2016 17:05:49 - Extension Details...
09/02/2016 17:05:49 - 	Identifier      : 5fb7364d-2e8c-44a4-95eb-2a382e30fec8
09/02/2016 17:05:49 - 	Name            : Web Essentials 2013.5
09/02/2016 17:05:49 - 	Author          : Mads Kristensen
09/02/2016 17:05:49 - 	Version         : 2.6.36
09/02/2016 17:05:49 - 	Description     : Adds many useful features to Visual Studio for web developers. Requires VS2013 Update 4 or 5
09/02/2016 17:05:49 - 	Locale          : en-US
09/02/2016 17:05:49 - 	MoreInfoURL     : http://vswebessentials.com/
09/02/2016 17:05:49 - 	InstalledByMSI  : False
09/02/2016 17:05:49 - 	SupportedFrameworkVersionRange : [0.0,2147483647.2147483647]
09/02/2016 17:05:49 - 
09/02/2016 17:05:50 - 	Supported Products : 
09/02/2016 17:05:50 - 		Microsoft.VisualStudio.Pro
09/02/2016 17:05:50 - 			Version : [12.0.31101,13.0)
09/02/2016 17:05:50 - 
09/02/2016 17:05:50 - 	References      : 
09/02/2016 17:05:50 - 
09/02/2016 17:05:50 - Searching for applicable products...
09/02/2016 17:05:50 - Found installed product - Microsoft Visual Studio Express 2012 for Windows Phone
09/02/2016 17:05:50 - Found installed product - Microsoft Visual Studio Ultimate 2013
09/02/2016 17:05:50 - Found installed product - Microsoft Visual Studio Premium 2013
09/02/2016 17:05:50 - Found installed product - Microsoft Visual Studio Professional 2013
09/02/2016 17:05:50 - Found installed product - Microsoft Visual Studio 2013 Shell (Integrated)
09/02/2016 17:05:50 - Found installed product - Global Location
09/02/2016 17:05:50 - VSIXInstaller.NoApplicableSKUsException: This extension is not installable on any currently installed products.
   at VSIXInstaller.App.InitializeInstall()
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()

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How is this? It says its looking for VS.pro, says it finds it, but that it can't find any installable products...???