Geometry server convex hull issue

[EdX1]

We've been trying to use a geometry server to calculate a convex hull of geometries, however our request gives a 400 error. This is even seen in the example request found at 

https://developers.arcgis.com/rest/services-reference/enterprise/convex-hull.htm

For reference this is the URL using the tasks URL:

http://tasks.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer/convexHull?geometries={%2...

Does anyone know what is causing the error?

[AnjulPandey]

Hello,

It is recommended that you create a geometry service object for use within your applications.

var geometryService = new esri.tasks.GeometryService("https://utility.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer");

//calculate the convex hull
          var points = dojo.map(features,function(feature){
            return feature.geometry;
          });
          geometryService.convexHull(points,function(result){
            var symbol;
            switch(result.type){
              case "point":
                symbol = new esri.symbol.SimpleMarkerSymbol();
                break;
              case "polyline":
                symbol = new esri.symbol.SimpleLineSymbol();
                break;
              case "polygon":
                symbol = new esri.symbol.SimpleFillSymbol();
                break;
            }
            map.graphics.add(new esri.Graphic(result,symbol));
          },function(error){
            console.log("An error occured during convex hull calculation");
          });