Json serialized messages wont get published to the broker. about mqttnet HOT 3 OPEN

using System;
using Newtonsoft.Json;
using MQTTnet;
					
public class Program
{
    public static void Main()
    {
        var m = JsonConvert.SerializeObject("Hello");
		
        var message = new MqttApplicationMessageBuilder()
            .WithTopic("Hans")
            .WithPayload(m)
            .Build();
        Console.WriteLine(message);
    }
}

public class Function1
{
    private readonly ILogger<Function1> _logger;

    public Function1(ILogger<Function1> logger)
    {
        _logger = logger;
    }

    [Function("Function1")]
    public async Task<IActionResult> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req)
    {
        const string HOST_URL = "xxx-xxx";
        const int PORT = 8883;
        const string TOPIC = "xxxxx";
        string username = "xxxxx";
        string randomName = Path.GetRandomFileName().Replace(".", string.Empty);

        IEnumerable<X509Certificate2> certList = new[]
        {
            new X509Certificate2("./certficate.pfx", "pass")
        };

        var factory = new MqttFactory();
        var client = factory.CreateMqttClient();

        var options = new MqttClientOptionsBuilder()
            .WithTcpServer(HOST_URL, PORT)
            .WithCredentials(username)
            .WithClientId(randomName)
            .WithCleanSession()
            .WithTlsOptions(o => o.WithClientCertificates(certList))
            .Build();

        // Serialize an object instead of a simple string
        var payloadObject = new { Message = "Hello" };
        var m = JsonConvert.SerializeObject(payloadObject);
        _logger.LogInformation(m); // This logs as expected

        try
        {
            await client.ConnectAsync(options, req.HttpContext.RequestAborted);
            var message = new MqttApplicationMessageBuilder()
                .WithTopic(TOPIC)
                .WithPayload(System.Text.Encoding.UTF8.GetBytes(m)) // Ensure the payload is correctly encoded
                .Build();

            await client.PublishAsync(message, req.HttpContext.RequestAborted);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to handle MQTT operation.");
            return new StatusCodeResult(StatusCodes.Status500InternalServerError);
        }
        finally
        {
            if (client.IsConnected)
            {
                await client.DisconnectAsync();
            }
        }

        _logger.LogInformation("C# HTTP trigger function processed a request.");
        return new OkObjectResult("Welcome to Azure Functions!");
    }
}