Javascript library failing to load 404 status

@model CheckTimeLine.Models.SelectOption
@{
    ViewBag.Title = "Home Page";
}

<h2>TimeLine</h2>

<!-- CSS -->

@section scripts{

    <!-- CSS -->
    <script src="~/Scripts/vis.min.js"></script>
    <!-- JS -->
    <link href="~/Content/vis.min.css" rel="stylesheet" />

    <script type="text/javascript">

        $(document).ready(function () {


            $.ajax({
                type: "GET",
                url: "GetAll",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: ChartVis,
                error: OnError

            });


            function ChartVis(response) {
                // DOM element where the Timeline will be attached
                var container = document.getElementById('visualization');

                // Create a DataSet (allows two way data-binding)
                var items = new vis.DataSet(response);

                // Configuration for the Timeline
                var options = {};

                // Create a Timeline
                var timeline = new vis.Timeline(container, items, options);
            }
            function OnError(response) {
                alert("Error !");
            }


        })

    </script>

}
<div id="visualization"></div>

vis.js:20107 Uncaught Error: Property "start" missing in item [object Object]
    at new o (vis.js:20107)
    at n.<anonymous> (vis.js:18462)
    at Array.forEach (<anonymous>)
    at n._onUpdate (vis.js:18439)
    at n.setItems (vis.js:18292)
    at o.setItems (vis.js:40905)
    at new o (vis.js:40826)
    at Object.ChartVis [as success] (Index:91)
    at fire (jquery-3.4.1.js:3291)
    at Object.fireWith [as resolveWith] (jquery-3.4.1.js:3421)