Style is not done loading: Mapbox GL JS

The problem is that you are adding the layer to the map before the map is loaded. Be sure you are attaching the tile source and the style layer in the load event handler.

afterMap.on('load', function() {
  afterMap.addSource("points", {
    "type": "geojson",
    "data": nyGeo
  })
  afterMap.addLayer({
    "id": "points",
    "type": "symbol",
    "source": "points",
    "layout": {
      "icon-image": "{icon}-15",
      "text-field": "{title}",
      "text-font": ["Open Sans Semibold", "Arial Unicode MS Bold"],
      "text-offset": [0, 0.6],
      "text-anchor": "top"
    }
  });
});