Making button activate update with boolean

Hey so I have been searching for a long time and I'm sorry if someone already asked something similar. But I am trying to make my code work so that when I press my button is will active the update when true. In void start when I set timerOn = true; the code works but when I set it to false so that when the button is clicked and sets timerOn to true it doesn't work, but I know the value reached update because my Debug.Log shows the message (under the else if)...I hope what I am asking makes sense...please help I have been stuck for hours :(

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class CountdownTimer : MonoBehaviour
 {
     [SerializeField] Text countdownText;
     public AudioSource audioData;
     public Button m_timer1;
 
     private bool timerOn;
     
     float minutes = 0;
     float seconds = 3;
     float miliseconds = 0;
 
     void Start()
     {
         audioData = GetComponent<AudioSource>();
 
         timerOn = false;
 
         Button btn = m_timer1.GetComponent<Button>();
         btn.onClick.AddListener(ClickBtn);
     }
 
     public void ClickBtn()
     {
         //Debug.Log("doesthiswork???!!");
         timerOn = true;
         Update();
     }
 
     public void Update()
     {
         if (timerOn == true)
         {
             if (minutes <= 0 && seconds <= 0 && miliseconds <= 0)// timerOn = false
             {
                 timerOn = false;
                 //Debug.Log("CurrentTime = 0");
                 Music_Play();
 
             }
 
             else if (miliseconds <= 0)
             {
                 Debug.Log("ithasreachedthisstage");
                 if (seconds <= 0)
                 {
                     minutes--;
                     seconds = 59;
                 }
 
                 else if (seconds >= 0)
                 {
                     seconds--;
                 }
 
                 miliseconds = 100;
             }
 
             miliseconds -= Time.deltaTime * 100;
 
             countdownText.text = string.Format("{0}:{1}", minutes, seconds);
         }
       
     }
 
     void Music_Play() //this works, now make the button work!!!
     {
         audioData.Play();
         //Debug.Log("musicon");
     }
 }