ListView Grouping of ObservableCollection does not display any grouped items

Hello everyone,

I am having a really hard time getting the groups to display on my listview. I used the guide posted by @JamesMontemagno
[
motzcod.es/post/94643411707/enhancing-xamarinforms-listview-with-grouping
Here is what I have:

ViewModel:

public async Task LoadEventLists()
        {
            if (IsBusy)
                return; 
            IsBusy = true;    
            var error = false;

            try
            {    
                var feedString = string.Empty;
                using (var httpClient = new HttpClient())
                {
                    var feed = "http://api.gcm.li/events/index.xml";
                    feedString = await httpClient.GetStringAsync(feed);    
                }    
                var newItems = await ParseEvents(feedString);    
                if (EventsItems.Count == 0) {
                    foreach (var item in newItems) {
                        EventsItems.Add(item);
                    }
                } else if (EventsItems.Count > 0) {    
                    var oldItems = EventsItems.ToList();
                    List<CalendarModel> newList = newItems.Except(oldItems, new CalendarComparer()).ToList();    
                    foreach (var item in newList)
                        EventsItems.Add(item);    
                }

                var sorted = from events in EventsItems
                    orderby events.Date
                    group events by events.EventSort into eventGroup
                    select new Grouping<string, CalendarModel>(eventGroup.Key, eventGroup);

                EventsGrouped = new ObservableCollection<Grouping<string, CalendarModel>>(sorted);
            }
            catch
            {
                error = true;    
            }    
            if (error)
            {
                var page = new ContentPage();
                await page.DisplayAlert("Error", "Unable to load upcoming events.", "OK");    
            }
            IsBusy =
                false;    
        }

        private async Task<List<CalendarModel>> ParseEvents(String rss)
        {

            return await Task.Run (() => {
                var xdoc = XDocument.Parse (rss);    
                var id = 0;    
                return (
                    from item in xdoc.Descendants ("event")
                    select new CalendarModel {                      
                        Date = (string)item.Element ("date"),
                        EventName = (string)item.Element ("event_name"),
                        StartTime = (string)item.Element("time_string"),
                        Location = (string)item.Element("location"),
                        Description = Regex.Replace((string)item.Element("event_description"), @"<[^>]*>", String.Empty),
                        LeaderName = (string)item.Element("leader_name"),
                        Id = id++,
                    }).ToList();
            });

        }

Model:

public class CalendarModel : INotifyPropertyChanged
    {
        public int Id { get; set; }
        public int Year { get; set; }
        public int Month { get; set; }
        public int Day { get; set; }
        public string Date { get; set; }
        public string EventName { get; set; }
        public string StartTime { get; set; }
        public string EndTime { get; set; }
        public string Location { get; set; }

        public string EventSort
        {
            get 
            {
                if (string.IsNullOrWhiteSpace(Date) || Date.Length == 0)
                    return "?";

                return Date.ToString().ToUpper();
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string name)
        {
            if (PropertyChanged == null)
                return;
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }

My View:

public class UpcomingEventsView : BaseView
    {
        private UpcomingEventsViewModel _viewModel
        {
            get { return BindingContext as UpcomingEventsViewModel; }
        }

        public UpcomingEventsView ()
        {
            BindingContext = new UpcomingEventsViewModel();
            ToolbarItems.Add(new ToolbarItem("search", "ic_today.png", async () => 
                {
                    await Navigation.PopModalAsync();
                }));

            var memberList = new ListView ();

            memberList.IsPullToRefreshEnabled = true;
            memberList.ItemsSource = _viewModel.EventsGrouped;
            memberList.IsGroupingEnabled = true;
            memberList.GroupDisplayBinding = new Binding("Key");
            memberList.GroupShortNameBinding = new Binding("Key");
            if(Device.OS != TargetPlatform.WinPhone)
                memberList.GroupHeaderTemplate = new DataTemplate(typeof(HeaderCell));
            memberList.HasUnevenRows = true;

            var cell = new DataTemplate(typeof(TextCell));
            cell.SetBinding(TextCell.TextProperty, "EventName");
            cell.SetBinding(TextCell.DetailProperty, "StartTime");

            memberList.ItemTemplate = cell;
            //Set Bindings 
            memberList.SetBinding<UpcomingEventsViewModel>(ListView.IsRefreshingProperty, vm => vm.IsBusy, BindingMode.OneWay); 
            memberList.SetBinding<UpcomingEventsViewModel>(ListView.RefreshCommandProperty, vm => vm.LoadEventsCommand);

            Content = memberList;
        }

        protected override async void OnAppearing()
        {           
            base.OnAppearing();
            _viewModel.LoadEventsCommand.Execute(null);
        }
    }

My issue is that nothing shows on the listview. The EventsItems add to the listview just fine, but the grouping will not. I'm not sure what I am doing wrong, but I could really use some help right about now. Thanks.