Background color and structure disappear when enabling GUI Canvas

I'm trying to create a simple pause menu which gets shown when the user presses escape while in game. My structure of canvas and sub-objects looks like this:

My script (C#) looks like this, it's attached to the gameController empty object in the root of the objects hierarchy:

 public class MenuController : MonoBehaviour {
     public Canvas pauseCanvas;
 
 
     void Start () {
     }
     
     void Update () {
         if(Input.GetKey(KeyCode.Escape)) {
             Debug.Log("escape pressed");
             pauseCanvas.enabled = true;
         }
     }
 }

==> For variable pauseCanvas I dragged the object with name 'gui' (the Canvas) to the variable input in the Inspector window. I disable the Canvas by default in the Inspector and the enable it using above code, which results in the background and button layout and such being gone.

When I press Escape this is what I want to see: http://i.imgur.com/RoXUH7a.png

This is what I get: http://i.imgur.com/nPA6eF8.png

Hope anyone can help, thanks in advance!