Loading scene from assetbundle (url)

I want to load the scene using www but it fails to download and shows a null. I'm not sure why it doesn't download.

 using UnityEngine;
 using System.Collections;
 using AssetBundles;
 
 
 public class loadingscene : MonoBehaviour
 {
     public string sceneAssetBundle;
     public string sceneName;
     public string url;
     
     // Use this for initialization
     IEnumerator Start ()
     {    
         yield return StartCoroutine(Initialize() );
         
         // Load level.
         yield return StartCoroutine(InitializeLevelAsync (sceneName, true) );
     }
     
     // Initialize the downloading url and AssetBundleManifest object.
     protected IEnumerator Initialize()
     {
         // Don't destroy this gameObject as we depend on it to run the loading script.
         DontDestroyOnLoad(gameObject);
         // With this code, when in-editor or using a development builds: Always use the AssetBundle Server
         // (This is very dependent on the production workflow of the project. 
         //     Another approach would be to make this configurable in the standalone player.)
         #if DEVELOPMENT_BUILD || UNITY_EDITOR
         AssetBundleManager.SetSourceAssetBundleURL(url);
         //    AssetBundleManager.SetDevelopmentAssetBundleServer ();
         #else
         // Use the following code if AssetBundles are embedded in the project for example via StreamingAssets folder etc:
         AssetBundleManager.SetSourceAssetBundleURL(Application.dataPath + "/");
         // Or customize the URL based on your deployment or configuration
         /AssetBundleManager.SetSourceAssetBundleURL("http://www.MyWebsite/MyAssetBundles");
         #endif
         
         // Initialize AssetBundleManifest which loads the AssetBundleManifest object.
         var request = AssetBundleManager.Initialize();
         
         if (request != null)
             yield return StartCoroutine(request);
     }
     
     protected IEnumerator InitializeLevelAsync (string levelName, bool isAdditive)
     {
         WWW www = WWW.LoadFromCacheOrDownload (url, 1);
         yield return www;
         if (www.error != null) {
             print ("WWW donwload had an error : " + url + " " + www.error);
                 //Debug.Log("");
             }
         AssetBundle bundle = www.assetBundle;
         Debug.Log(www.assetBundle.mainAsset);
 
         // This is simply to get the elapsed time for this phase of AssetLoading.
         float startTime = Time.realtimeSinceStartup;
         
         // Load level from assetBundle.
         AssetBundleLoadOperation request = AssetBundleManager.LoadLevelAsync(sceneAssetBundle, levelName, isAdditive);
         if (request == null)
             yield break;
         yield return StartCoroutine(request);
         // Calculate and display the elapsed time.
         float elapsedTime = Time.realtimeSinceStartup - startTime;
         Debug.Log("Finished loading scene " + levelName + " in " + elapsedTime + " seconds" );
         bundle.Unload(false);
         // Frees the memory from the web stream
         www.Dispose();
     }
 }