Getting exception right after use of HttpClient

So I'm using Microsoft.Http.Net, with ModernHttpClient, and I'm getting an unhandled exception everytime I trigger a PostAsync() method....
In this case, the BaseUrl is a local API I'm developing with Laravel, but it also doesn't work with jsonplaceholder...

`
using ModernHttpClient;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace CSA
{
[XamlCompilation(XamlCompilationOptions.Compile)]

public partial class Login : ContentPage
{
    HttpClient Client = new HttpClient(new NativeMessageHandler());
    public class AuthData {

        public string username { get; set; }
        public string password { get; set; }

    }

    public Login()
    {
        InitializeComponent();
        logo_csa.Source = ImageSource.FromResource("CSA.Images.photo.jpg");
        NavigationPage.SetHasNavigationBar(this, false);
        Client.DefaultRequestHeaders.Add("Accept", "application/json");
    }

    private async void Button_Clicked(object sender, EventArgs e)
    {
        user.IsEnabled = false;
        pass.IsEnabled = false;
        LoginBtn.IsEnabled = false;
        Indicator.IsVisible = true;
        AuthFail.IsVisible = false;

        var AuthAttempt = new AuthData();
        AuthAttempt.username = user.Text;
        AuthAttempt.password = pass.Text;
        var content = JsonConvert.SerializeObject(AuthAttempt);
        var Url = Application.Current.Properties["baseUrl"] + "/login";
        var response = await Client.PostAsync(Url, new StringContent(content)); //This is the line where I get the crash
        //var data = JsonConvert.DeserializeObject(content);
        //await DisplayAlert("llala", data.ToString() , "OK");


    }
}

}
`