Sharepoint 2013 Themable CSS not working

I'm attempting to use the Themable features in SharePoint 2013 and can't figure out what I'm doing wrong

I'm creating a file called ResponsiveTheme.css at /Style Library/en-us/Themable/ResponsiveTheme.css

The contents of this file right now are pretty simple

/*[RecolorImage(themeColor:"PageBackground", method:"Filling", includeRectangle:{x:251,y:101,width:20,height:18})] */
background-image: url("/_layouts/15/images/spcommon.png?rev=23");

In my masterpage, I'm adding the following code in the html masterpage

<!--MS:<SharePoint:CssRegistration Name="&lt;% $SPUrl:~sitecollection/Style Library/~language/Themable/ResponsiveTheme.css %gt;" runat="server">-->
<!--ME:</SharePoint:CssRegistration>-->

I have also tried adding the After="core15.css" and EnableCssTheming="true" to the above tag with no luck

The broswer return a 404 when trying to access /_catalogs/theme/Themed/3F6D5C95/ResponsiveTheme-5F12C7E7.themedcss?ctag=27

Can anyone give me a tip on how to get this to work, or possibly point me to where any logs related to the theming engine reside in SharePoint

Thanks