NullRefrenceException error

I am getting this error

NullReferenceException: Object reference not set to an instance of an object
chucknorris1+d__4.MoveNext () (at Assets/chucknorris1.cs:41)

when running my script. The debug log returns the desired text, but the text is not shown in the textmeshrpo field (it is not assigned to _chuckjoke)

using UnityEngine;
using UnityEngine.Networking;
using System.Collections;
using SimpleJSON;
using TMPro;

public class chucknorris1 : MonoBehaviour

{
    private TextMeshPro _chuckJoke;

    private const string URL = "https://api.chucknorris.io/jokes/random";

    private void start()
    {
        _chuckJoke = FindObjectOfType<TextMeshPro>();// GameObject.Find("OutputArea").GetComponent<InputField>();
    }
    public void GenerateRequest()
    {
        StartCoroutine(ProcessRequest(URL));
    }

    private IEnumerator ProcessRequest(string uri)
    {
        using (UnityWebRequest request = UnityWebRequest.Get(uri))
        {

            yield return request.SendWebRequest();

            if (request.isNetworkError)
            {
                Debug.Log(request.error);
            }
            else
            {
                Debug.Log(request.downloadHandler.text);

                JSONNode itemsData = JSON.Parse(request.downloadHandler.text);

                Debug.Log("The generated item is: 

Name: " + itemsData[“value”]);
_chuckJoke.SetText($“Jkoe is :{itemsData[“value”]}”);
}
}
}
}

  1. private void Start() must be writed correctly
  2. you should use debugger to see which variable returns null i personally thing it causes of ;

_chuckJoke = FindObjectOfType<TextMeshPro>(); or
Debug.Log("The generated item is: Name: " + itemsData["value"]); _chuckJoke.SetText($"Jkoe is :{itemsData["value"]}"); this variables, you should check them if they returns null or not.

@kaveheng Check your game object, I think you had more than one game object that is attached with game component TextMeshPro. You have to understand the different between FindObjectOfType and FindObjectsOfType. The “s” meant array. If you had more than one object with TextMeshPro, Unity will fail to find the object and it will return error as fail to instancing the object and return object as null reference.
Try to be more specific in you game object search with either direct link or use more advance code.