Null Reference Exception on scheduler CallBack

A team member sent me his project which was using scheduler and getting the same error I have below. I made some suggestion that I was unsure was the reason, and then started a controller and view to test using the scheduler. I followed one of the tutorials and I got the same issue at the same place; the CallBack which ends up on line 19:

public ActionResult Backend()
{
return new Scheduler().CallBack(this);
}

I'm uploading the controller and view in case it helps.

System.NullReferenceException was unhandled by user code
HResult=-2147467261
Message=Object reference not set to an instance of an object.
Source=DayPilot.Web.Mvc
StackTrace:
at DayPilot.Web.Mvc.Json.JsonData.op_Explicit(JsonData data)
at DayPilot.Web.Mvc.Json.JSONObject.getBoolean(String key)
at DayPilot.Web.Mvc.DayPilotScheduler.CallBack(Controller c)
at RAM.Controllers.misController.Backend() in C:\Users\wclark.IDIVAFB\Source\Workspaces\Workspace\RAM\RAM\Controllers\misController.cs:line 19
at lambda_method(Closure , ControllerBase , Object[] )
at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.ActionInvocation.InvokeSynchronousActionMethod()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
at System.Web.Mvc.Async.AsyncResultWrapper.End[TResult](IAsyncResult asyncResult, Object tag)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f()
InnerException: