Null Refernce Exception, OnMouseDown

Hi,

I'm getting the ever-so-common null reference exception error. Although, I can't for the life of me, figure out why. The error is as follows:

NullReferenceException: Object reference not set to an instance of an object Tile.OnMouseDown () (at Assets/Scripts/Tile.cs:32) UnityEngine.SendMouseEvents:DoSendMouseEvents(Int32)

Tile.cs is:

  public class Tile : MonoBehaviour 
  {
   
 public Vector2 GridPosition = Vector2.zero;

 private Renderer rend;
 private Color defaultColor;
     
 // Use this for initialization
 void Start () {
     rend = GetComponent<Renderer>();
     defaultColor = rend.material.color;
 }
 
 // Update is called once per frame
 void Update () {
 
 }

 void OnMouseEnter()
 {
     rend.material.color = Color.red;
 }
 void OnMouseExit()
 {
     rend.material.color = defaultColor;
 }
 void OnMouseDown()
 {
     Debug.Log("Executes!");
     Debug.Log(this);
     GameManager.Instance.moveCurrentPlayer(this);
     Debug.Log("Maybe?");
 }
 }

and GameManager.cs:

 public class GameManager : MonoBehaviour {
 
     public static GameManager Instance;
     public GameObject TilePrefab;
     public GameObject CharacterPrefab;
 
     public int MapSize = 11;
     int PlayerIndex;
 
     List<List<Tile>> map = new List<List<Tile>>();
     List<Player> players = new List<Player>();
 
     void awake()
     {
         Instance = this;
     }
 
     // Use this for initialization
     void Start ()
     {
         GenerateMap();
         GeneratePlayers();
     }
     
     // Update is called once per frame
     void Update ()
     {
         players[PlayerIndex].TurnUpdate();
 
     }
     public void NextTurn()
     {
         if (PlayerIndex + 1 < players.Count)
         {
             PlayerIndex++;
         }
         else
         {
             PlayerIndex = 0;
         }
     }
     public void moveCurrentPlayer(Tile destinationTile)
     {
     Debug.Log(destinationTile);
     Debug.Log("Player Index: " + PlayerIndex + " : " + players[PlayerIndex]);
     players[PlayerIndex].moveDestination = destinationTile.transform.position + 1.5f * Vector3.up;
     }
 }

Background:

1. Tile.cs is a component of a "tile" prefab.

2. These tiles are generated at run time (this works as intended)

3. The Mouse Enter/Exit stuff changes the colour of the tiles as intended

4. Debug.Log("Executes") runs, than the null reference exception.

5. all of the debugs in moveCurrentPlayer Do Not run, nor does Debug.Log("Maybe?");

When I click on the selected tile it gives me above stated error. But, if I debug.log(this) it gives me the Object Name. Additionally, I checked to make sure Players[PlayerIndex] wasn't the issue by commenting it out adding Debug.Log(destinationTile.transform.position) and got the same error. If anyone can help I would be eternally grateful!