- Make certain that the .less files are marked as Content in VS
- Make certain that its not a less compilation problem. Do this by running the dotless compiler manually from the command line.
- Perhaps you need to add the .less mime type mapping in IIS / your web config file:
<system.webServer>
<staticContent>
<mimeMap fileExtension=".less" mimeType="text/css" />
</staticContent >
</system.webServer>