Observable Collection now showing in ListView

So I know this is a very basic question but i am stuck i dont know why.

    var list = await AppointmentApi.GetAppointment(Guid.Parse(Setting.Id));
                if (list == null)
                {
                    return;
                }
                var model = new AppointmentViewModel();
                foreach (var appointment in list)
                {
                    model.Appointments.Add(appointment);
                }
                AppointmentListView.ItemsSource = model.Appointments;

`
<?xml version="1.0" encoding="utf-8" ?>



<ListView.ItemTemplate>





</ListView.ItemTemplate>

      </StackLayout>
    </ContentPage>

`

`
public class AppointmentViewModel
{
public ObservableCollection Appointments { get; set; }

        public AppointmentViewModel()
        {
            Appointments = new ObservableCollection<Appointment>();
        }


    }

`