Parse Exception System.AggregateException

Hi

I'm new with parse and I'm getting troubles to integrate the API in my project principal to run any query.

Here is my code:

 IEnumerator UpdatePosition()
 {
     var query = ParseObject.GetQuery ("User").WhereEqualTo("username",usrID.text);    
     var task = query.FirstAsync ();

     while(!task.IsCompleted) yield return null;

     if (task.IsFaulted || task.IsCanceled){
         Debug.Log("Cannot get the user "+task.Exception.Message);
     }else{
         ParseObject result = task.Result;
         Debug.Log ("===> "+result.Get<string>("parent"));
     }
     
 }

Always the code goes to 'task.IsFaulted' and the display is:

Cannot get the user Exception of type 'System.AggregateException' was thrown.

Here I am sure that usrID.text contain a valid username which has just one record and I'm using Unity 5.0.2f1 and Parse 1.5.3

So anyone can give me a light on this

Thank you very much