Unity Physics2D.OverlapAreaAll not picking up any colliders

Hi, I have the following relatively simple code.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class GameRTSController : MonoBehaviour
 {
     private Vector3 startPosition; 
     void Update() {
 
         if (Input.GetMouseButtonDown(0)) {
             startPosition = Input.mousePosition;
         }
 
         if (Input.GetMouseButtonUp(0)) {
             Debug.Log(startPosition + " " + Input.mousePosition);
             Collider2D[] collider2DArray = Physics2D.OverlapAreaAll(startPosition, Input.mousePosition);
             Debug.Log(collider2DArray);
             foreach (Collider2D collider2D in collider2DArray) {
                 Debug.Log(collider2D);
             }
         }
 
     }
 }

But I'm unable to detect any of the colliders in the scene.

Any advice?