Error mapping theme to template

Greetings,
Keep getting a "Value cannot be null. Parameter name: type" error when I try to map a custom theme to a custom template. Perhaps its my path to my theme?:

"~/App_Data/Sitefinity/WebsiteTemplates/Homepage/App_Themes/Homepage/main.css"

Not sure what to try next. Looking for some suggestions. Thanks in advance.

Hi Chris,

If I understand you correctly your are trying to add your theme to website and use it in your custom template. Correct me if I am wrong. Please consult our designer's guide - the section related to the registration of themes.

Greetings,
Victor Velev
the Telerik team

Hi Victor,
I have looked at the documentation, and been using as I'm new to Sitefinity. I've followed all steps of uploading a custom template and theme. My template works, but the CSS isn't being applied...which is when I looked into mapping the theme to the template.  

Hello Chris,

Please create a screenshots of your site structure so I can get a better picture of the situation. If for example your master page is in folder App_Data\Sitefinity\WebsiteTemplates\YourTemplate\App_Themes\MyTheme and is called mymaster and the css is in WebsiteTemplates\YourTemplate\App_Themes\MyTheme\Global\mycss.css you can reference to it by adding the following lines in your head tag of the master page:

Hi Victor,
I added the link to the style sheet manually, but its not loading any of the styles. Here's is my strucuture:

WebsiteTemplates
- Homepage
-- App_Master
    --- homepage.master
-- App_Themes
    --- Homepage
       ---- Global
        ----- main.css



And here is what I am using to manually pull in my style sheet:

<link href="/Sitefinity/WebsiteTemplates/Homepage/App_Themes/Homepage/Global/main.css" type="text/css" rel="stylesheet" />

Hi Chris,

Can you open a support ticket and send me the theme files, so I can install it locally and diagnose the problem.

Kind regards,
Victor Velev
the Telerik team