playerprefs dont load for menu toggle

 using UnityEngine;
 using UnityEngine.UI;
 
 public class Instructor_toggle : MonoBehaviour
 {
 
     private bool togglevalue;
     private Toggle toggle;
 
 
     // Use this for initialization
     void Start()
     {
         toggle = GetComponent<Toggle>(); //get the toggle
         togglevalue = toggle.isOn; //get the toggle's value
         toggle.onValueChanged.AddListener((value) => { changeinstructor(value); });//add listener to the toggle
         togglevalue = PlayerPrefsX.GetBool("instructor"); //get the setting
     }
     public void changeinstructor(bool thevalue)
     {
         Toolbox.instructor_enabled = thevalue; //set the actual instructor to changed value
         PlayerPrefsX.SetBool("instructor", togglevalue); //set the setting
         PlayerPrefs.Save(); //save the setting
     }
 }

the above code doesn't work properly. I have this script attached to a toggle in my pause menu ui, and the problem im having is that the value always reverts to it's default, off, whenever i exit the game and re-enter the game. I want this toggle to be persistent across game sessions. what puzzles me is that this is set up in exactly the same way as an audio volume slider on the same menu which works perfectly as i want it to.