Unknown reason for NullReferenceException error

Just need someone to read over this code and see if they can source the reason for the NullReferenceException error

using System;
using UnityEngine;

public class Enemy : MonoBehaviour
{
    Vector3 prevPos;

    GameObject player;
	Player playerScript;

    public Vector3 targetPosition;
	
	public Transform turretF, turretB, turretT;
	
	void Start()
	{
		player = GameObject.Find("Player");
		playerScript = player.GetComponent<Player>();
        prevPos = transform.position;

        turretB = transform.Find("turretB");
        turretT = transform.Find("turretT");
        turretF = transform.Find("turretF");
    }
	
	void Update()
	{

        targetPosition = new Vector3(player.transform.position.x, turretB.position.y, player.transform.position.z);

        turretB.LookAt(targetPosition);
    }
}

The following line is the one that returns the reference error:

targetPosition = new Vector3(player.transform.position.x, turretB.position.y, player.transform.position.z);

Thanks in advance!

targetPosition = new Vector3(player.transform.position.x, turretB.position.y, player.transform.position.z);

“player” is already referenced in Start(), so it can’t be null. That only leaves “turretB”. Now you have to find out why “transform.Find(“turretB”);” doesn’t find the GameObject.

If you don’t know how to use a debugger, some Debug.Log() outputs of involved variables are usually enough to spot what’s going on.