A routine question: do you see anything in the browser console? 

I know that for some certain routes you have to specify default.aspx as content output

For instance /EPiServer/cms/admin/ does not return the admin view but /EPiServer/cms/admin/default.aspx does.

This should however not be part of your problem...

Nada in Console.

Nada in log file.

/default.aspx makes it throw 404 "A public action method 'default.aspx' was not found on controller 'EPiServer.Cms.Shell.UI.Controllers.Internal.VisitorGroupsController'."

/index = empty blank

Something is killling it softly, it probably something stupido.

How does your <episerver.shell> and <location path="EPiServer"> configuration look like in Web.config?

Looks good Mattias, compared with working sites and no diff.

File system access rights? :)

Full access no diff.

I have same behavior on staging server, so its not just local.

Have i Messed up SiteViewEngine : RazorViewEngine? i don't find anything there too though

hos does your RouteTable look like?

The RouteTable looks as good as you do Jedi Master Iljuconoks.

39 items.

you have items like

{[ModuleRouteCollection RoutePath="~/EPiServer/EPiServer.GoogleAnalytics/2.1.1", Routes=[EPiServer.GoogleAnalyticsepi-googleanalytics]]}

{[ModuleRouteCollection RoutePath="~/EPiServer/EPiServer.DeveloperTools", Routes=[]]}'

{[ModuleRouteCollection RoutePath="~/episerver", Routes=[EPiServer.Packaging.UI,EPiServer.Search.Cms,AddOn.Edit.ContextMenuOpenInNewTab,EPiServer.DeveloperTools,Shell,CMS,EPiServer.Cms.TinyMce,EPiServer.Forms.UI,EPiServer.Forms,EPiServer.GoogleAnalytics]]}

What more should i be looking for?

If you reach out for developer support service for this, I would be happy to look into this :) 

Cred to Episerver Dev Support,

After debugging Episerver Source they found out the root cause of this issue is SiteViewEngine is inserted to ViewEngines in the first position:

ViewEngines.Engines.Insert(0, new SiteViewEngine()); // which is default in alloy template to optimize view resolving when using DisplayFor/PropertyFor

So it overrides the episerver ViewEngine.
You can use this instead of:

ViewEngines.Engines.Add(new SiteViewEngine());

We did made some customization in viewengine so maybe not so suprising.

Regards

Hey I deserve a bit of credit as well ;) (telling you to reach out for Dev support) 

To tweak view resolving a little bit, you could insert it right before WebFormViewEngine (if using default MVC setup):

var webFormViewEngine = ViewEngines.Engines.FirstOrDefault(ve => ve.GetType() == typeof(WebFormViewEngine));

if (webFormViewEngine != null)
{
    var webFormViewEngineIndex = ViewEngines.Engines.IndexOf(webFormViewEngine);
    
    ViewEngines.Engines.Insert(webFormViewEngineIndex, new SiteViewEngine());
}
else
{
    ViewEngines.Engines.Add(new SiteViewEngine());
}