Troubleshooting basic movement problems

Hi there, I'm very new to unity and programming (so sorry if this i posted in the wrong place), but have a little experience with c++, I have followed several tutorials by quil18, but im having trouble with one particular thing. I have followed his tilemap tutorial :

I'm having trouble implementing a 'selection indicator' to highlight wight tile the mouse is hovering over. In the tutorial he uses a slightly transparent cube, raycast from the mousepointer to the tilemap mesh, get the coordinates from the mesh (hit info point), a little maths to determine which tile you are pointing to, then move the cube to that tile. My only problem is the cube isnt moving, i have put in debug logs, the correct tile is being shown, the transform position line runs, but the cube doesn't move. Im sorry if this is a really blindingly simple error but its quite frustrating. My code below:

Code (CSharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4. [RequireComponent(typeof(TileMap))]
5. public class TileMapMouse : MonoBehaviour {
6.  
7. TileMap _tileMap;
8. Vector3 currentTileCoord;
9. public Transform selectionIndicator;
10.  
11.     void Start(){
12.         _tileMap = GetComponent<TileMap>();
13.     }
14.  
15.         // Update is called once per frame
16.     void Update () {
17.  
18.         Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
19.         RaycastHit hitInfo;
20.  
21.         if ( collider.Raycast(ray , out hitInfo, Mathf.Infinity) ){
22.             int x = Mathf.FloorToInt(hitInfo.point.x / _tileMap.tileSize);
23.             int z = Mathf.FloorToInt(hitInfo.point.z / _tileMap.tileSize);
24.             Debug.Log ("Tile"+ x + "," + z);
25.             currentTileCoord.x = x;
26.             currentTileCoord.z = z;
27.             selectionIndicator.transform.position = currentTileCoord * 5f;
28.         }
29.  
30.         else{
31.             //stuff
32.         }
33.     }
34. }
35.  

Edit:format