unity dictionary with array as keys causes problems

I am using a dictionary to store coordinates and their respective heights to generate random terrain using a diamond square algorithm. However, when I try accessing keys of the dictionary, I keep getting "KeyNotFoundException: The given key was not present in the dictionary.". Here is the code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.Tilemaps;
 
 public class TerrainFractal : MonoBehaviour
 {
     private int SizePower = 3;
     private int height = 0;
     private int width = 0;
     private float seed = 0f;
     private float randomHeight = 0;
 
     Dictionary < List<int>, float> WorldMap = new Dictionary< List<int>, float>();
 
     // Start is called before the first frame update
     void Start()
     {
         height = Mathf.RoundToInt(Mathf.Pow(2, SizePower)) + 1;
         width = height;
         GenerateFractalMap();
     }
 
     public void GenerateFractalMap() {
         for (int x = 0; x < width; x ++ ) {
             for (int y = 0; y < height; y ++ ) {
                 var coordinates = new List<int> {x, y};
                 WorldMap[coordinates] = 0;
             }
         }
         
         randomHeight = Random.Range(0f, 10f);
         WorldMap[new List<int> {0, 0}] = randomHeight;
         WorldMap[new List<int> {0, height - 1}] = randomHeight;
         WorldMap[new List<int> {width - 1, 0}] = randomHeight;
         WorldMap[new List<int> {width, height - 1}] = randomHeight;
         for (int i = 0; i < 1; i++ ) {
             DiamondStep(i);
             Debug.Log(WorldMap);
         }
     }
 
     public void SquareStep(int SizePower, Dictionary <int[], float> Map, int itteration) {
         int numberOfPoints = Mathf.RoundToInt(Mathf.Pow(2, itteration));
         int NumberOfLines = numberOfPoints * 2 - 1;
         int coordX = 0;
         int coordY = 0;
     }
 
     public void DiamondStep(int itteration) {
         int numberOfPoints = Mathf.RoundToInt(Mathf.Pow(2, itteration));
         int NumberOfLines = numberOfPoints;
         int coordX = 0;
         int coordY = 0;
         var coords = new int[2];
         int displacement = Mathf.RoundToInt(Mathf.Pow(2, SizePower - itteration - 1));
         int multiple = Mathf.RoundToInt(Mathf.Pow(2, SizePower - itteration));
         float newHeight = 0;
         float randomDisplacement = 0;
         for (int l = 0; l < NumberOfLines; l ++) {
             coordX = displacement + l * multiple;
             for (int p = 0; p < numberOfPoints; p ++) {
                 coordY = displacement  + p * multiple;
                 Debug.Log(WorldMap[new List<int> {0,0}]);
                 newHeight += WorldMap[new List<int> {coordX - displacement, coordY - displacement}];
                 newHeight += WorldMap[new List<int> {coordX - displacement, coordY + displacement}];
                 newHeight += WorldMap[new List<int> {coordX + displacement, coordY - displacement}];
                 newHeight += WorldMap[new List<int> {coordX + displacement, coordY + displacement}];
 
                 newHeight = newHeight / 4;
                 randomDisplacement = Random.Range(-1f, 1f);
                 newHeight += randomDisplacement;
                 WorldMap[new List<int> {coordX, coordY}] = newHeight;
             }
         }
     }
     // Update is called once per frame
     void Update()
     {
 
     }
 }

The error occurs at line 66: Debug.Log(WorldMap[new List {0,0}]); I have checked, and the dictionary seems to contain a key of the form [0, 0], so this leaves me very confused.

Thank you for your help.