ASP.NET Core Web API - How to resolve BasicAuthentication was not authenticated. Failure message: No contains header

In ASP.NET Core-6 Web API project, I am implementing Basic Authentication. I have this code:

Model:

public class User
{
    public int Id { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
}

Service:

public interface IUserService
{
    public bool isUser(string username, string password);
}

public class UserService : IUserService
{
    private readonly ApplicationDbContext _dbContext;        
    public UserService(
        ApplicationDbContext dbContext,
        )
    {
        _dbContext = dbContext;
    }

    public bool isUser(string username, string password)
    {
        var userFind = _dbContext.User.Where(u => u.Username == username && u.Password == password);
        if (userFind.Any()) return true;
        else return false;
    }
}

Then I have this Basic Auth Handler code in the helpers.

BasicAuthHandler:

public class BasicAuthHandler : AuthenticationHandler<AuthenticationSchemeOptions>
{
    private readonly IUserService _repository;
    public BasicAuthHandler(IOptionsMonitor<AuthenticationSchemeOptions> options,
                            ILoggerFactory loggerFactory,
                            UrlEncoder urlEncoder,
                            ISystemClock systemClockm,
                            IUserService repository)
        : base(options, loggerFactory, urlEncoder, systemClockm)
    {
        _repository = repository;
    }
    protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        if (!Request.Headers.ContainsKey("Authorization")) 
            return AuthenticateResult.Fail("No contains header");

        bool result = false;

        try
        {
            var AuthHeader = AuthenticationHeaderValue.Parse(Request.Headers["Authorization"]);
            var credentialBytes = Convert.FromBase64String(AuthHeader.Parameter);
            var credentials = Encoding.UTF8.GetString(credentialBytes).Split(new[] { ':' }, 2);
            //get parameters in array format
            var username = credentials[0];
            var password = credentials[1];
            result = _repository.isUser(username, password);
        }
        catch(Exception)
        {
            return AuthenticateResult.Fail("Some ERROR");
        }
        if (!result)
            return AuthenticateResult.Fail("Error User Name or Password ");

        var claims = new Claim[]
        {
            new Claim(ClaimTypes.NameIdentifier, "id"),
             new Claim(ClaimTypes.Name, "user")
        };
        var identity = new ClaimsIdentity(claims, Scheme.Name);
        var principal = new ClaimsPrincipal(identity);
        var ticket = new AuthenticationTicket(principal, Scheme.Name);
        return AuthenticateResult.Success(ticket);
    }
}

Program.cs:

builder.Services.AddScoped<IUserService, UserService>();
builder.Services.AddAuthentication("BasicAuthentication")
    .AddScheme<AuthenticationSchemeOptions, BasicAuthHandler>("BasicAuthentication", null);

When I run the application, the page was blank, and I got this error in the log file:

BasicAuthentication was not authenticated. Failure message: No contains header

Which indicates that it stops here:

if (!Request.Headers.ContainsKey("Authorization")) 
    return AuthenticateResult.Fail("No contains header");

bool result = false;

How do I resolve it?

Thanks