Did you put the code properly ? if you are using WordPress, you are supposed to paste the code in "appearance>editor>there should be column from the right side, chose Theme Header and paste the code right after <head>, it should look like this :
<head>
<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<script>
(adsbygoogle = window.adsbygoogle || []).push({
google_ad_client: "ca-pub-111111111111111",
enable_page_level_ads: true
});
</script>
once done, click update file and wait another couple of days....