Azure Blob File is Detected Not Exist While It Actually Exists

I want to move a video file from Azure Blob Storage to Sharepoint directly using C#. The code below does not work because there is a problem when getting the blobStream. I have ensured that my containerName and blobName are correct. However, when I checked the existence of the blobClient using blobClient.ExistAsync(), it always returns false. Does anyone know why a blob file cannot be detected while it actually exists in the Azure Blob Storage? Thanks in advance.

using System;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using Azure.Core;
using Azure.Identity;
using Microsoft.Graph;

namespace ZoomRecordingHelper
{
    public class GraphHandler
    {
        public GraphServiceClient GraphClient { get; set; }

        public GraphHandler()
        {
            var clientId = "";
            var clientSecret = "";
            var tenantId = "";

            var options = new TokenCredentialOptions
            {
                AuthorityHost = AzureAuthorityHosts.AzurePublicCloud
            };

            var clientSecretCredential = new ClientSecretCredential(tenantId, clientId, clientSecret, options);
            var scopes = new[] { "https://graph.microsoft.com/.default" };

            GraphClient = new GraphServiceClient(clientSecretCredential, scopes);
        }

        public async Task UploadFileToSharePoint(string siteId, string driveId, string fileName, Stream fileStream)
        {
            try
            {
                var uploadUrl = $"https://graph.microsoft.com/v1.0/sites/{siteId}/drives/{driveId}/items/root:/{fileName}:/content";

                using (var httpClient = new HttpClient())
                {
                    var accessToken = await GetAccessTokenAsync();
                    httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
                    using (var httpRequest = new HttpRequestMessage(HttpMethod.Put, uploadUrl))
                    {
                        httpRequest.Content = new StreamContent(fileStream);
                        httpRequest.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
                        using (var response = await httpClient.SendAsync(httpRequest))
                        {
                            response.EnsureSuccessStatusCode();
                            Console.WriteLine("File uploaded successfully.");
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error uploading file: {ex.Message}");
            }
        }
        
       public async Task<Stream> GetBlobStreamAsync(string connectionString, string containerName, string blobName)
        {
            var blobServiceClient = new BlobServiceClient(connectionString); // my conn string : DefaultEndpointsProtocol=https;AccountName=databinuscampussolution;AccountKey=xxxxxxxx;EndpointSuffix=core.windows.net

            var containerClient = blobServiceClient.GetBlobContainerClient(containerName); // my containerName : bm5

            var blobClient = containerClient.GetBlobClient(blobName); // my blobName : zoom/recording/BBS/2024-8-7/93116161045.mp4

            var isExist = await blobClient.ExistsAsync(); //always return false

        if (isExist.Value)
        {
            Console.WriteLine($"Start downloading blob {blobName}");
            var response = await blobClient.DownloadAsync();
            Console.WriteLine($"Finish downloaded blob {blobName}");

            return response.Value.Content;
        }
        else
        {
            Console.WriteLine($"Blob {blobName} does not exist in container {containerName}.");
            return null;
        }
        }

        private async Task<string> GetAccessTokenAsync()
        {
            var clientId = "";
            var clientSecret = "";
            var tenantId = "";

            var options = new TokenCredentialOptions
            {
                AuthorityHost = AzureAuthorityHosts.AzurePublicCloud
            };

            var clientSecretCredential = new ClientSecretCredential(tenantId, clientId, clientSecret, options);
            var tokenRequestContext = new TokenRequestContext(new string[] { "https://graph.microsoft.com/.default" });

            var accessTokenResult = await clientSecretCredential.GetTokenAsync(tokenRequestContext);

            return accessTokenResult.Token;
        }
    }
}