What has changed is how Google delivers Auto Ads.
But:
1. Any time you make a change in the AdSense scripts it can take up to several hours for the changes to be applied to your site, given how the ads are selected by Google's scripts - although usually the ads just disappear for a few hours...
2. The code you display above is incomplete. It should look like this:
Code:
<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<ins class="adsbygoogle"
style="display:block"
data-ad-client="ca-pub-xxxxxxxxxxxxxxxx"
data-ad-slot="xxxxxxxxxx"
data-ad-format="auto"
data-full-width-responsive="true"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>
That is the script you would normally insert in the ad placements html boxes (some people split it up to optimize page loading, with the first part loaded in the head.../head section).
3. But if you are/were using Auto ads, there is a second script, probably added into PAGE_CONTAINER between the head and the /head tags.
You would need to remove that part AND go back to the Google Auto Ads page at
How to set up Auto ads - AdSense Help to turn off the Auto Ads options for your "URL Group".