UnityAds won't show anymore after 2 ads

Unity Services
1

voidOnGUI() {
if(GUI.Button(newRect(10, 10, 150, 50), Advertisement.IsReady() ? “Show Ad” : “Waiting…”)) {
Advertisement.Show(null, newShowOptions {
resultCallback = result => {
Debug.Log(result.ToString());
}
});
}

if(GUI.Button(newRect(220, 10, 150, 50), “Get”) ){
Advertisement.Initialize (“62635”);
}
}

Android device can not show after 2ads

2

Probably there is no more available ads for user since watching same ads is not possible. In some country’s there is no much campaigns.