Inspector won't update with new variables.,Variables don't seem to update on inspector

Probably a really simple newbie question but hey ho. I've been following a tutorial on Youtube by Jimmy Vegas, and I've managed to put together a script but I had to add another variable to it. I've updated the script, and there are no compiler errors but the inspector won't update with the new variable.

 public class Quest001 : MonoBehaviour
 {
 
     public int TextBoxOnCheck = 0;
     public GameObject MessageBox;
     public GameObject TextBox;
     public string TextMessage;
     public GameObject QuestBox;
     public GameObject QuestText;
     public string QuestName;
     public GameObject QuestItemToShow;

Its variable QuestItemToShow that I'm struggling with, everything else shows up fine.