Endless Jumper Platform Spawning Script

I have made this script for infinite Jumper game and I want the platforms to spawn according to the camera height in random positions and to the get deactived again to reduce lag.

But I cant get the platforms to actually spawn. If anybody could maybe look over my script and tell me what i am doing wrong it would be very nice.

 ublic class Platform 
 {
     public GameObject platformObj;
     public string platformType;
     public Platform (GameObject obj, string t)
     {
         platformObj = obj;
         platformType = t;
     }
 }
 
 public class PlatformManagerScript : MonoBehaviour 
 {
     //PROPERTIES
     [Header("Platform Prefabs")]
     public GameObject[] platform;
     List<GameObject> platformBank = new List<GameObject>();
 
     [Header("Number of Platforms in Screen at once")]
     public int maxPlatforms = 100;
     public float spawnPlatformsTo;
     public float platformOffset;
     [Header("Screenlimitations")]
     public float screenBorderLeft;
     public float screenBorderRight;
 
     [HideInInspector]
     private float platformCheck;
     [HideInInspector]
     public Transform player;
     [HideInInspector]
     public float playerHeightY;
 
 
     void Start ()
     {
         player = GameObject.FindGameObjectWithTag("Player").transform;
 
 
 
         int numCopies = maxPlatforms * 3;
         for (int i = 0; i < numCopies; i++) 
         {
             for (int j = 0; j < platform.Length; j++) 
             {
                 GameObject o = (GameObject) Instantiate(platform[j], new Vector3(-20,-20,0),platform[j].transform.rotation);
                 o.SetActive(false);
                 platformBank.Add(o);
                 Debug.Log("Banked Platforms");
             }
         }
 
         ShuffleList();
 
     }
 
     void Update ()
     {
         playerHeightY = player.position.y;
         if (platformCheck < playerHeightY) 
             PlatformPositionManager ();
         UnactivatePlatform ();
 
         
     }
 
     void ShuffleList ()
     {
         System.Random rand = new System.Random ();
         int r = platformBank.Count;
         while (r > 1) 
         {
             r--;
             int n = rand.Next(r+1);
             GameObject val = platformBank[n];
             platformBank[n] = platformBank[r];
             platformBank[r] = val;
         }
     }
 
     void PlatformPositionManager ()
     {
         platformCheck = player.position.y + platformOffset;
         PlatformSpawner(platformCheck + platformOffset);
     }
 
     void PlatformSpawner (float floatValue)
     {
         float y = spawnPlatformsTo + 2.5f;
 
         while (playerHeightY > 0) {
 
             float x = Random.Range (-2.78f, 0.14f);
             Vector3 posXY = new Vector3 (x, y, 0);
             for (int n = 0; n < platformBank.Count; n++) {
                 GameObject o = platformBank [n];
                 if (!o.activeSelf) 
                 {
                     o.transform.position = posXY;
                     o.SetActive(true);
                     n = platformBank.Count + 1;
                 }
             }
 
             y += Random.Range(1f, 4f);
             Debug.Log ("Moved Platform");
         }
 
         spawnPlatformsTo = floatValue;
     }
 
     void UnactivatePlatform ()
     {
         foreach (GameObject platform in platformBank) {
             if (platform.transform.position.y < playerHeightY - 15) 
             {
                 platform.SetActive(false);
             }
         }
     }
 
 }