I found a c# tutorial on youtube about speech recognition, the code runs without any error but, it does not respond to my voice input

I've been building an AI Speech Recognition program by looking at a tutorial from youtube and it runs proper;y without any errors. But it doesn't recognize my voice input. I'm using System.speech library. This is the code that I used

enter code here

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Speech.Synthesis;
using System.Speech.Recognition;

namespace VoiceBot
{
    public partial class Form1 : Form
    {
        SpeechSynthesizer s = new SpeechSynthesizer {};
        Choices list = new Choices {};


        public Form1()
        {

            SpeechRecognitionEngine rec = new SpeechRecognitionEngine { };

            list.Add(new string[] { "Hello", "How are you?", "What time is it?" });
            Grammar gr = new Grammar(new GrammarBuilder(list));

            try
            {
                rec.RequestRecognizerUpdate();
                rec.LoadGrammar(gr);
                rec.SpeechRecognized += rec_SpeachRecognized;
                rec.SetInputToDefaultAudioDevice();
                rec.RecognizeAsync(RecognizeMode.Multiple);
            }
            catch { retu; }


            s.SelectVoiceByHints(VoiceGender.Female);
            s.Speak("Hello, My name is voice bot, How may I help you?");
            InitializeComponent();
        }

        public void say(String h)
        {
            s.Speak(h);
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void rec_SpeachRecognized(object sender, SpeechRecognizedEventArgs e)
        {
            String r = e.Result.Text;

            //what you say
            if(r== "hello")
            {
                //what it says
                say("Hi");
            }

            if (r == "how are you?")
            {
                say("Great, and you?");
            }
        }
    }
}