PushSharp 4.0 - Namespace not recognized "PushBroker"

I have the following problem, I recently added the PushSharp 4.0 lib to my server to be able to send notifications to ios.

However with the code I have, I'm getting the following error:

  

the type namespace name 'PushBroker' could not be found

The code I have is the following:

using PushSharp;
using PushSharp.Core;
using PushSharp.Apple;

var push = new PushBroker();

try
{
   var appleCert = File.ReadAllBytes(test);//Server.MapPath(test));

   push.RegisterAppleService(new ApplePushChannelSettings(true, appleCert, _iphoneCertPasswordV2));

   push.QueueNotification(new AppleNotification()
                .ForDeviceToken(device)//the recipient device id
                .WithAlert("Mensagem a enviar")//the message
                .WithBadge(1)
                .WithSound("sound.caf")
   );
}
catch (Exception ex)
{
    throw ex;
}

Why do not you recognize PushBroker ? The same goes for below with AppleNotification() .