C# Advertisment every so many plays

Hey guys,

I'm trying to play an ad every so many new games. (My game is a play/die/retry type game).

My thinking is that I can establish an incremental adding integer like this:

 void Start () {
     
         numOfGames = PlayerPrefs.GetInt ("newGames");
         add1 = numOfGames += 1;
         PlayerPrefs.SetInt ("newGames", add1);
         PlayerPrefs.Save ();
 }

in another script I call the ads based on if the number of new games is a multiple of 4 like this:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.Advertisements;
 
 public class adsAtAnInterval : MonoBehaviour {
 
     [SerializeField] string gameID = "00MYID00";
 
     public int gameSessionInt;
     public int modulo;
     
 
     void Awake(){
 
         Advertisement.Initialize (gameID, true);
 
     }
 
     // Use this for initialization
     void Start () {
 
         gameSessionInt = PlayerPrefs.GetInt ("newGames");
         modulo = gameSessionInt % 4;
         advertAtInterval ();
     }
 
     void advertAtInterval(){
 
         if (modulo == 0 && Advertisement.IsReady()) {
 
             Advertisement.Show("rewardedVideo");
 
         }
 
     }
 
 }

Regardless if modulo == 0, my ads are not showing. Anyone have any thoughts? Much appreciated! -A