Xperience 13 Content tree-based routing with MVC Areas

We upgraded our MVC full framework site to xperience 13. The site uses MVC areas and I am wondering if that may be why the content tree-based routing is not behaving as expected? I have set up Xperience 13 as a new site and had no problem with the content tree-based routing then, it's only on this upgraded MVC site with areas that I am hitting problems.

In the MVC site I have this route defined in RoutingAssemblyInfo.cs:

[assembly: RegisterPageRoute(TestPageType.CLASS_NAME, typeof(TestPageController), ActionName = "Index")]

The above references all resolve fine according to Visual Studio. The Kentico generated classes and the controller all look good.

In Global.asax I am enabling the feature:

    protected void Application_Start()
    {
    // Gets the ApplicationBuilder instance
    // Allows you to enable and configure selected Xperience MVC integration features
    ApplicationBuilder builder = ApplicationBuilder.Current;

    // Enables content tree-based routing
    builder.UsePageRouting();

    ApplicationConfig.RegisterFeatures(builder);

    AreaRegistration.RegisterAllAreas();

    ...

The TestPageController never gets hit when I enter the URL that is defined in the Page URL field in the CMS. The MVC site serves up a not found page.

If anyone has any ideas they would be much appreciated, thanks!