Script only runs once?

I have a button that draws a gui box, and a button that shuts the box, however after I shut the box, I can no longer open it again from the open box button.

Any ideas?

  using UnityEngine;
     using System.Collections;
  
     public class Gui : MonoBehaviour {
     bool boxcheck1 = false;
     bool boxcheck2 = false;
     bool boxcheck3 = false;
     bool boxcheck4 = false;
     bool shutboxcheck1 = false;
  
     //Campaign box
     void OnGUI() {
     if (GUI.Button(new Rect(250, 700, 90, 20), "Campaign")){
     boxcheck1 = true;
     }
     if (boxcheck1 == true) {
     boxcheck2 = false;
     boxcheck3 = false;
     boxcheck4 = false;
     GUI.Box(new Rect(10, 10, 1008, 680), "");
             
     if (GUI.Button(new Rect(870, 650, 110, 20), "Close window")){
     shutboxcheck1 = true;
     }
     if (shutboxcheck1 == true) {
     boxcheck1 = false;
     boxcheck2 = false;
     boxcheck3 = false;
     boxcheck4 = false;
     }
     }