Getting a routing error it seems after upgrading CMS to 11.15.1 when trying to browse directory contents after enabling it in IIS.  Had been running CMS 11.2.1.

{"$id":"1","Message":"An error has occurred.","ExceptionMessage":"The object has not yet been initialized. 
Ensure that HttpConfiguration.EnsureInitialized() is called in the application's startup code after all other initialization code.
","ExceptionType":"System.InvalidOperationException","StackTrace":"   
at System.Web.Http.Routing.RouteCollectionRoute.get_SubRoutes()\r\n   
at System.Web.Http.Routing.RouteCollectionRoute.GetRouteData(String virtualPathRoot, HttpRequestMessage request)\r\n   
at System.Web.Http.WebHost.Routing.HttpWebRoute.GetRouteData(HttpContextBase httpContext)"}