SignalR is not working with my Xamarin form.

I made Api for SignalR using Asp.net api. it is working in Api side.

but it is not working when i run with Xamarin App.

I put Api code below:

public class ChatHub : Hub
{
    public void Send(string name, string message)
    {
        // Call the broadcastMessage method to update clients.
        Clients.All.broadcastMessage(name, message);
    }

    public void SendMessage(string message, int color, string username)
    {
        Clients.All.UpdateChatMessage(message, color, username);
    }
   }

I put Xamarin Cs code below:

public partial class Chat : ContentPage
 {
    HubConnection hubConnection;
    public Chat()
    {
        InitializeComponent();

        DoRealTimeSuff();
    }

    async private void DoRealTimeSuff()
    {
        SignalRChatSetup();
        await SignalRConnect();
    }

    private void SignalRChatSetup()
    {
       // var ip = "localhost";
        hubConnection = new HubConnectionBuilder().WithUrl($"https://750e01e568f9.ngrok.io/Home/Chat/").Build();


        hubConnection.On<string, string>("UpdateChatMessage", (message, user) =>
        {
            var UpdatedChatMessage = $"{user} says {message}";
            this.MessageHolder.Text += UpdatedChatMessage + "\n";
        });

    }

    async Task SignalRConnect()
    {
        try
        {
            await hubConnection.StartAsync();
        }
        catch (Exception ex)
        {
            // Connection failed. Fail graciously.
        }
    }

    private async void ButtonSendEventHandler(object sender, System.EventArgs e)
    {
        await SignalRSendMessage(this.UserName.Text, this.UserMessage.Text);


    }

    async Task SignalRSendMessage(string name, string message)
    {
        try
        {
            await hubConnection.InvokeAsync("Send", name, message);
        }
        catch (Exception ex)
        {
            // Send failed. Fail graciously.
        }
    }

   }

Xaml code.

  <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         xmlns:d="http://xamarin.com/schemas/2014/forms/design"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
         mc:Ignorable="d"
         x:Class="Gmdemo.Views.Chat">
    <ContentPage.Content>
     <StackLayout Orientation="Vertical" Margin="50">
        <Entry Placeholder="User" x:Name="UserName" />
        <Entry Placeholder="Message" x:Name="UserMessage" />
        <Button Text="Send Message" Clicked="ButtonSendEventHandler" />
        <Label x:Name="MessageHolder" />
    </StackLayout>
 </ContentPage.Content>
  </ContentPage>

I have no idea why my Xamarin program could not connect with that Api.
When i check "hubConnection = new HubConnectionBuilder().WithUrl($"https://750e01e568f9.ngrok.io/Home/Chat/").Build();".

there is nothing that i get any values. I have no idea which part is wrong.