Audio not playing after OnTriggerStay is applied to the scripts (Driving Simulator Project)

Hello. I am making a driving simulator for my project.

The code below is for Speed Limit scene.

When drivers drive within a certain speed, they will be given warnings to reduce their speed if they break the speed limit.

Here I am using colliders. Everything is working fine, however I found out that the Audio is not playing.

This happen after I added OnTriggerStay onto the codes, can anyone check my codings if anything is wrong? Thank you. The deadline for this project is next week.

   using System.Collections;
     using System.Collections.Generic;
     using UnityEngine;
     using UnityEngine.UI;
 
 public class SpeedWarning : MonoBehaviour {
 
     float carSpeed;
 
     private GameObject car;
     private RCCCarControllerV2 carController;    
     private Rigidbody rigid;
 
     public Text slowDown;
     public Text good;
     public  AudioSource SpeedWarningSound;
     //public float goodTime = 2;
 
     void Start(){
         carController = GetComponent<RCCCarControllerV2> ();
         SpeedWarningSound = GetComponent<AudioSource> ();
         rigid = GetComponent<Rigidbody>();
     }
     
     void OnTriggerEnter (Collider car) {
         if (car.gameObject.name == ("40kmh_Collider")) {
             if (carController.speed > 40) {
                 SpeedWarningSound.Play ();
                 slowDown.enabled = true;
                 good.enabled = false;
                 Debug.Log ("Laju");
 
             } else if (carController.speed < 40) {
                 SpeedWarningSound.Stop ();
                 slowDown.enabled = false;
                 good.enabled = true;
                 //Destroy (good, goodTime);
                 Debug.Log ("masuk ikut speed limit ni");
                 //good
             } 
         }
     }
 
     void OnTriggerStay (Collider car) {
         if (car.gameObject.name == ("40kmh_Collider")) {
             if (carController.speed > 40) {
                 //StartCoroutine (PlayWarn ());
                 SpeedWarningSound.Play ();
                 slowDown.enabled = true;
                 good.enabled = false;
                 Debug.Log ("Increase ya belaju");
 
             } else if (carController.speed < 40) {
                 //StartCoroutine (StopWarn ());
                 SpeedWarningSound.Stop ();
                 slowDown.enabled = false;
                 good.enabled = true;
                 //Destroy (good, goodTime);
                 Debug.Log ("ubahnya pelahan");
                 //good
             } 
         }
     }
 
     void OnTriggerExit (Collider car) {
         if (car.gameObject.name == ("40kmh_Collider")) {
             SpeedWarningSound.Stop ();
             slowDown.enabled = false;
             good.enabled = false;
             Debug.Log ("yes");
 
         } else {
 
         }
 
     }

}