Problem with Checkpoint counting

I've made Checkpoint system, where a plane goes through rings and checkpoints are counted. It was done with OnGUI.

Recently I came across one of the Unity tutorials: http://unity3d.com/learn/tutorials/modules/beginner/live-training-archive/creating-a-jewel-miner-game

It crossed my mind that using UI -> Text was better than coding everything manually with OnGUI. I guess it would be more convenient and simpler to modify if I really wanted to do that in the future.

The problem is as follows: GameManager that is attached to Canvas on the right hand side shows CheckPointCount and TotalCheckpointCount correctly on any particular level. On the other hand on-screen checkpoint count is not changing it's numbers. It's always 0/2 with 2 being the amount of Checkpoints on the level. It was done with UI -> Text, scripts are attached. I think it's a problem with code.

Excerpt of code from GameManager.cs:

 void Start()
     {
         //Amount of checkpoints = Amount of checkpoints from parent folder
         TotalCheckpointCount = CheckpointParent.transform.childCount;
         CheckpointText.text = ("Checkpoints: " + CheckpointCount + "/" + TotalCheckpointCount);
     }
 
      //Checkpoint iteration
      public void AddCheckpoint()
     {
         CheckpointCount += 1;
         CheckpointText.text = ("Checkpoints: " + CheckpointCount + "/" + TotalCheckpointCount);
     }

And excerpt of code from Player.cs, when player is colliding with object:

  if (other.transform.tag == "Checkpoint")
         {
             manager.CheckpointCount += 1;
             Destroy(other.gameObject);
         }

I think I should do something with that CheckpointCount in Player.cs, but I'm not exactly sure how to tackle this. Change it with a reference to the AddCheckpoint class from GameManager perhaps? Any ideas would be greatly appreciated.