IE11 Enterprise Mode site list not working

I've configured the Enterprise Mode site list as directed in the following article

http://msdn.microsoft.com/en-us/library/dn640696.aspx

and set up the gpo to point to my site.  I've confirmed in my site's logs that the xml file is accessible.

However, it isn't working; none of the sites are launching in enterprise mode.  I notice that the CurrentVersion key in HKCU\Software\Microsoft\Internet Explorer\Main\EnterpriseMode has remained at 1 and is not updating.  I'm assuming that is the problem, but I can't figure out why it won't update.

Any advice?