How to play an audiosource and have a canvas message still show?

Basically what the title says. With the code below, when the audio plays, the text doesn't show up but shows up on the next click and the sound doesn't play. So, how do I get them to trigger at the same time?

 import UnityEngine.UI;
 import QuestManager1;

 var TextBoxOnCheck : int = 0;
 var MessageBox : GameObject;
 var TextBox : GameObject;
 var TextMessage : String;
 var QuestBox : GameObject;
 var QuestText : GameObject;
 var QuestName : String;
 var Sitting : GameObject;
 var SittingTalk : GameObject;
 var getcatpls : AudioSource;

     function OnMouseDown () {
    if (QuestManager1.canTalk == 1) {
    if (TextBoxOnCheck == 0) {
        //QuestItemToShow.SetActive(true);
        TextBoxOnCheck = 1;
        Sitting.SetActive(false);
        SittingTalk.SetActive(true);
        MessageBox.SetActive(true);
        TextBox.GetComponent.<Text>().text = TextMessage;
        QuestManager1.canGetCat += 1;
        QuestName = "Active Quest: Find Gerald's Cat";
        QuestText.GetComponent.<Text>().text = QuestName;
         yield WaitForSeconds (3);
            MessageBox.SetActive(false);
            SittingTalk.SetActive(false);
            Sitting.SetActive(true);

        } else {
            TextBoxOnCheck = 0;
            MessageBox.SetActive(false);
             Sitting.SetActive(false);
        SittingTalk.SetActive(true);
        getcatpls.Play();
            TextMessage = "Gerald: Please go get my cat, I need her to survive!";
            yield WaitForSeconds (4.5);
                           SittingTalk.SetActive(false);
            Sitting.SetActive(true);
            MessageBox.SetActive(false);
        }
        } else {
        Debug.Log("Can't talk to wizard yet");
        }

        }

 function Update() {
   if (Input.GetButtonDown("Submit")) {
   Slacking();
    }

   if (Input.GetButtonDown("Cancel")) {
    Slacking();
    }
 }

 function Slacking() {
 if (TextBoxOnCheck == 1) {
      MessageBox.SetActive(false);
      TextBoxOnCheck = 0;
       TextMessage = "Gerald: Please go get my cat, I need her to survive!";

       yield WaitForSeconds (4.5);
       MessageBox.SetActive(false);
            SittingTalk.SetActive(false);
            Sitting.SetActive(true);
   }
   }