Game object not enabled after SetActive(true).

Hi, I've a scene where I put a GameObject with a circle animated for the operations of loading. I have to active and deactive this GO in various points of my application so I put it in a singleton.

 public sealed class SingletonManagerUI
 {
 ....
 private static SingletonManagerUI instance = null;
 GameObject Loader {get;set;}
 public static SingletonManagerUI Instance{
         get{        
             lock(padlock){
                 if(instance == null){
                     instance = new SingletonManagerUI();
                 }
             return instance;
         }
 }
 public void SetLoader(GameObject Lo){
         Loader = Lo;
 }
 public GameObject GetLoader(){
     return Loader;
 }
 ...
 }

When I active the GO it isn't rendered in the scene. When the application start I put the GameObject with the loader in the scene:

 GameObject Loader = GameObject.FindGameObjectWithTag("LoaderProgress");
 SingletonManagerUI.Instance.SetLoader(Loader);

The scenario is the follow: the application start with the circle active and it works, I deactive it in a point of my application. In another point of my application I active it but it doesn't rendered. Where is my mistake? I'm sure that circle is in the right position in the scene. This is the istruction that I use:

 SingletonManagerUI.Instance.GetLoader().SetActive(true);

The method GetLoader() return a GameObject.

Thanks a lot guys.