MapBox markers not showing up - GeoJson at URL

Question

I am attempting to move my GeoJson from inline jscript to a URL to evaluate how it improves performance for maps with a lot of markers (3,000+). However, I have been unable to get my markers to display on the map, and would appreciate a fresh set of eyes. The url to my test page is here: http://webapps.fhsu.edu/ksherp/testmapbox.aspx The GeoJson file is linked

     <script>
            mapboxgl.accessToken = 'pk.eyJ1IjoidHRhZ2dhcnQiLCJhIjoiY2lwZmp0emR2MDA1YnRhbmQ2aW8xdm9wZCJ9.XMq3bMhOjRit7wR3q7oIgQ';
            var map = new mapboxgl.Map({
                container: 'map', // container id
                style: 'mapbox://styles/ttaggart/cj3ohbccw00192rlrtj18zdmv', //stylesheet location
                center: [-98.328809, 38.5], // starting position
                zoom: 5 // starting zoom
           // , maxZoom: 8 // limit max zoom extent
            });

            var url = 'http://webapps.fhsu.edu/ksherp/geojson/3.geojson';
            map.on('load', function () {
                window.setInterval(function () {
                    map.getSource('markers').setData(url);
                }, 2000);

                map.addSource('markers', { type: 'geojson', data: url });

                map.addLayer({
                    "id": "markers",
                "type": "symbol",
                "source": "markers",
                "layout": {
                "icon-image": "{marker-symbol}-11"
                }
                });
            });

            // When a click event occurs near a marker icon, open a popup at the location of
            // the feature, with description HTML from its properties.
            map.on('click', function (e) {
                var features = map.queryRenderedFeatures(e.point, { layers: ['markers'] });
                if (!features.length) {
                    return;
                }
                var feature = features[0];
                // Populate the popup and set its coordinates
                // based on the feature found.
                var popup = new mapboxgl.Popup()
                    .setLngLat(feature.geometry.coordinates)
                    .setHTML(feature.properties.description)
                    .addTo(map);
            });
            // Use the same approach as above to indicate that the symbols are clickable
            // by changing the cursor style to 'pointer'.
            map.on('mousemove', function (e) {
                var features = map.queryRenderedFeatures(e.point, { layers: ['markers'] });
                map.getCanvas().style.cursor = (features.length) ? 'pointer' : '';
            });
            map.addControl(new mapboxgl.NavigationControl());
            map.addControl(nav, 'top-right');

Answer 1

Your test page is not working, it shows Server Error in '/ksHerp' Application..

Using your code without modification I had no issues displaying the markers:

If your page is working again and you're still having this issue, you could check the browser console if your GeoJSON file is not loaded because of a CORS error or some browser restrictions using mixed-content (http/https). Some links which might be helpful:

https://www.mapbox.com/help/cors-errors/

How to get Chrome to allow mixed content?