TFS 2013 work item change event listener is not working - plugins

Question

I'm trying to listen workitem changes in TFS 2013. I created a c# project and build successfully this code below. Then dll located in tfs server:
I restart machine and I checkin a class in tfs for test with a work item. When I control tfs server there is no any Log folder created in C disk like code. TfsEventHandler project builded with .net framework 4.5
My queston is, why plugin is not working?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.TeamFoundation.Common;
using Microsoft.TeamFoundation.Framework.Server;
using Microsoft.TeamFoundation.WorkItemTracking.Server;
using System.Diagnostics;
using System.IO;
namespace TfsEventHandler
{
public class WorkItemChangedEventHandler : ISubscriber
{
public string Name
{
get
{
return "WorkItemChangedEventHandler";
}
}
public SubscriberPriority Priority
{
get
{
return SubscriberPriority.Normal;
}
}
public EventNotificationStatus ProcessEvent(
TeamFoundationRequestContext requestContext,
NotificationType notificationType,
object notificationEventArgs,
out int statusCode,
out string statusMessage,
out Microsoft.TeamFoundation.Common.ExceptionPropertyCollection properties)
{
statusCode = 0;
properties = null;
statusMessage = String.Empty;
WriteLog("WorkItemChangedEventHandler1");
try
{
if (notificationType == NotificationType.Notification && notificationEventArgs is WorkItemChangedEvent)
{
WorkItemChangedEvent ev = notificationEventArgs as WorkItemChangedEvent;
int workItemId = Convert.ToInt32(ev.CoreFields.IntegerFields[0].NewValue);
WriteLog("WorkItemChangedEventHandler WorkItem " + ev.WorkItemTitle + " - Id " + workItemId.ToString() + " was modified");
EventLog.WriteEntry("WorkItemChangedEventHandler", "WorkItem " + ev.WorkItemTitle + " - Id " + workItemId.ToString() + " was modified");
}
}
catch (Exception)
{
}
return EventNotificationStatus.ActionPermitted;
}
public Type[] SubscribedTypes()
{
return new Type[] { typeof(WorkItemChangedEvent) };
}
public static void WriteLog(string strLog)
{
StreamWriter log;
FileStream fileStream = null;
DirectoryInfo logDirInfo = null;
FileInfo logFileInfo;
string logFilePath = "C:\\Logs\\";
logFilePath = logFilePath + "Log-" + System.DateTime.Today.ToString("MM-dd-yyyy") + "." + "txt";
logFileInfo = new FileInfo(logFilePath);
logDirInfo = new DirectoryInfo(logFileInfo.DirectoryName);
if (!logDirInfo.Exists) logDirInfo.Create();
if (!logFileInfo.Exists)
{
fileStream = logFileInfo.Create();
}
else
{
fileStream = new FileStream(logFilePath, FileMode.Append);
}
log = new StreamWriter(fileStream);
log.WriteLine(strLog);
log.Close();
}
}
}