We are afraid that the support is provided via forums only so the webex may not be an option. Moreover, a narrowed down sample will help us assist you efficiently without necessarily dealing with irrelevant details. Furthermore, you may try to pass basepath, where the HTML file exists, to the constructor of
HtmlLoadOptions class as under and then share if the CSS apply or not.
//We intend to demonstrate use of basepath/baseURL in first line here
Aspose.Pdf.HtmlLoadOptions objLoadOptions = new Aspose.Pdf.HtmlLoadOptions(dataDir);
Aspose.Pdf.Document doc = new Aspose.Pdf.Document(dataDir + "Test.html", objLoadOptions);
About temporary license, no evaluation limitations apply if temporary license is set successfully in your code so this is not a limitation.