Set Hierarchy Object Active from Instantiated Object

I have a Canvas that is Inactive in the Hierarchy. When an instantiated object (Object A) collides with a specific object in the $$anonymous$$erarchy (Object B) there is a script on Object B that will set the Canvas to active and set text to somet$$anonymous$$ng. That works fine.

But I want to do the same t$$anonymous$$ng with two objects that are instantiated (Objects A and C collide). I can't get Object A to reference the Canvas in the Hierarchy. I turned the Canvas into a prefab and linked the two objects that way, and it won't give me any errors, but when I call SetActive(true) from the instantiated Object A not$$anonymous$$ng happens.

I've also tried tagging the Canvas and FindGameObjectWithTag during Start() but that throws an error.

 // LevelExit.cs

 // T$$anonymous$$s Works
 void OnTriggerEnter(Collider other)
 {
     if (other.gameObject.tag == "Hero")
     {
         notice.gameObject.SetActive(true);
         noticeText.text = "Press 'A' to go to next Level!";
     }
 }

 // HeroScript.cs 

 //T$$anonymous$$s Doesn't
 
 public Canvas notice; // Prefab of canvas (already in $$anonymous$$erarchy)
 
 void OnTriggerEnter(Collider other)
     {
         if (other.gameObject.tag == "enemy")
         {
             notice.gameObject.SetActive(true);
             notice.GetComponentInC$$anonymous$$ldren<Text>().text = "You $$anonymous$$t an enemy";
         }
     }