Parse + FB Login

Question

I'm using Parse and their .NET SDK (WP8) to login into my application with a Facebook account. I wrote :

IEnumerable<string> permissions = new List<string>() {"user_about_me"};
try 
{
    ParseUser user = await ParseFacebookUtils.LogInAsync(browser, permissions);
}
catch (Exception e)
{
    System.console.Write("Error {0}", e.ToString());
}

But I catching an exception : "A task was canceled" I registered my app on http://developers.facebook.com, copy and paste everything (and Product ID from my app manifest).

Do you know what am I missing ?