В парсере на c# в переменная не получает нужное значение и становится null

вот код

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ScrapingDollarRate
{
    internal class Episode
    {
        public string OverallNumber { get; set; }
        public string Title { get; set; }
        public string Directors { get; set; }
        public string WrittenBy { get; set; }
        public string Released { get; set; }
    }
}



using HtmlAgilityPack;
using CsvHelper;
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Globalization;



namespace ScrapingDollarRate
{
    class Program
    {
        static void Main(string[] args)
        {
            // the URL of the target dollar rate page
            string url = "https://www.banki.ru/products/currency/usd/";

            var web = new HtmlWeb();
            // downloading to the target page
            // and parsing its HTML content
            var document = web.Load(url);
            var nodes = document.DocumentNode.SelectNodes("div[class = 'Flexbox__sc-wtbhrg-0 hrHAlf']");

            List<Episode> episodes = new List<Episode>();
            foreach (var node in nodes)
            {
                // add a new Episode instance to
                // to the list of scraped data
                episodes.Add(new Episode()
                {
                    OverallNumber = HtmlEntity.DeEntitize(node.SelectSingleNode("div[class = 'Text__sc-j452t5-0 hDxmZl']").InnerText),
                    Title = HtmlEntity.DeEntitize(node.SelectSingleNode("div[class = 'Text__sc-j452t5-0 bCCQWi']").InnerText)
                });

            }

            // initializing the CSV file
            using (var writer = new StreamWriter("output.csv"))
            using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
            {
                // populating the CSV file
                csv.WriteRecords(episodes);
            }
        }
    }
}

выскакивает ошибка System.NullReferenceException: 'Object reference not set to an instance of an object.'