VerifyTotp always fails

1.VS 2022：New ASP.NET Core Web (Model-Model-Controller)
2.Install-Package Otp.NET, Install-Package QRCoder
3.HomeController.cs
using Microsoft.AspNetCore.Mvc;
using System.Diagnostics;
using Web.Models;
using OtpNet;
using QRCoder;
using System.Text;

public class HomeController : Controller
{
private readonly ILogger _logger;
private const string Secret = "JBSWY3DPEHPK3PXP";
private const string BaseUser = "test";
private const string Issuer = "demo";

public HomeController(ILogger<HomeController> logger)
{
    _logger = logger;
}

public IActionResult Index()
{
    return View();
}

public IActionResult Qrcode()
{
    string uriString = new OtpUri(OtpType.Totp, Secret, BaseUser, Issuer).ToString();

    using QRCodeGenerator qrGenerator = new();
    using QRCodeData qrCodeData = qrGenerator.CreateQrCode(uriString, QRCodeGenerator.ECCLevel.Q);
    using PngByteQRCode qrCode = new(qrCodeData);
    {
        byte[] qrCodeImage = qrCode.GetGraphic(20);
        return File(qrCodeImage, "image/jpeg");
    }
}

public IActionResult Validate(string code)
{
    var totp = new Totp(Encoding.UTF8.GetBytes(Secret));
    var verificationWindow = VerificationWindow.RfcSpecifiedNetworkDelay;
    var isValid = totp.VerifyTotp(code, out long timeWindowUsed, verificationWindow);
    return Content(isValid ? "Success" : "Fail");
}

}
4.Views/Home/Index.cshtml
@{
ViewData["Title"] = "Home Page";
}
<div class="text-center">
<h1 class="display-4">Welcome</h1>
<img src="/Home/Qrcode" style="width: 300px;" />
<form action="/Home/Validate" method="post">
Code: <input name="code" />
<input type="submit" value="Validate" />
</form>
</div>
5.run
6.Scan the QR code using APP Authenticator
7.Enter totp code, VerifyTotp always fails

Start by reproducing the supplied ASP.NET Core sample, then inspect HomeController.cs, especially the Qrcode and Validate actions, alongside Views/Home/Index.cshtml. Compare the QR code's generated value with the code passed to VerifyTotp. Done means identifying why the scanned code is rejected and recording a verified fix or precise compatibility diagnosis.