Android : AssetBundle loading model is not showing in mobile

0 I'm loading 3d model from server url and using assetbundle but when i load the model in unityeditor it's working fine and the 3d model of cube is displaying proper. But when i load the model in android mobile the model is not displaying in the screen.

 IEnumerator GetAssetBundle() {

         string bundleURL = url;

         Debug.Log (bundleURL);
         using (WWW www = WWW .LoadFromCacheOrDownload(bundleURL, Version)) {
             yield return www;
             Debug.Log (Version);

             if (www .error != null)
                 throw new UnityException("WWW Download had an error: " + www .error);

             AssetBundle bundle = www .assetBundle;
             if (AssetName == "") {
                 Debug.Log ("null");
                 mBundleInstance = Instantiate (bundle.mainAsset) as GameObject;
                 mBundleInstance.transform.parent = imageTarget.transform;
                 mBundleInstance.transform.localPosition = new Vector3(0,0,0);


             }
             else {
                 Debug.Log ("not null");
                 mBundleInstance = Instantiate(bundle.Load (AssetName)) as GameObject;
             }
         }
     }