Android and Ruby: Volley Listener isn't called but the server receive the request

I have an Android app and I'm trying to send a GET request to my Ruby server and I'm using the Volley Library for it.

My Activity has the following code:

UserController.findUser(Utils.URL_findUser + userEmail, new ServerCallback() {
    @Override
    public void onSuccess(JSONObject result) {
        //do something
    }

    @Override
    public void onFailure(VolleyError error) {
        //do something
    }
});

The method findUser:

public static void findUser(String URL, final ServerCallback callback) {

    JsonObjectRequest objectRequest = new JsonObjectRequest(Request.Method.GET, URL, null, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            callback.onSuccess(response);
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            callback.onFailure(error);
        }
    });

    MySingleton.getInstance().addToRequestQueue(objectRequest);
}

The server receive the request, like this:

Started GET "/users/test@gmail.com" for 127.0.0.1 at 2017-11-24 16:32:49 -0200
Processing by UsersController#show as HTML
  Parameters: {"email"=>"test@gmail.com"}
  User Load (2.3ms)  SELECT  "users".* FROM "users" WHERE "users"."email" = $1 LIMIT $2  [["email", "test@gmail.com"], ["LIMIT", 1]]
{"controller"=>"users", "action"=>"show", "email"=>"test@gmail.com"}
Completed 200 OK in 17ms (Views: 1.0ms | ActiveRecord: 2.3ms)

But the Response.Listener and Response.ErrorListener is never called.

My function in Rails:

  def show
    render :json => @usuario
  end

I have no idea about what is happening because no error message appear. By the way, when I do the same in a browser I receive the anwer.

I'm using Volley because I need sessions management. Someone know if exists another library that can do the same?

UPDATE:

I did the same with OkHttp Library and it worked. But I really would like to use the Volley and understand why this is happening