MapHttpAttributeRoutes not working

I have a Web API 2 project that is now throwing the following error message:

The inline constraint resolver of type 'DefaultInlineConstraintResolver' was unable to resolve the following inline constraint: 'id'.

I am wondering why it started doing this now since my WebApiCOnfig hasn't changed (See below)

public static void Register(HttpConfiguration config)

{             // Web API configuration and services

config.Filters.Add(new GeneralActionFilter());

config.Filters.Add(new GeneralExceptionFilterAttribute());

// Web API routes - Allows Actions to define a route via Attribute

config.MapHttpAttributeRoutes();

config.Routes.MapHttpRoute(

name: "DefaultApi",

routeTemplate: "api/{controller}/{id}",

defaults: new { id = RouteParameter.Optional } );

None of my api calls are working now. I was hoping that the config.MapHttpAttributeRoutes(); would help, but it seems like it is not doing anything at all even though I have routes such as this: [Route("students/{studentId:int}/homeschoolverifications")]

I'll appreciate any help you can give me...