Since a period of more than 10 days, it turns out that Google stopped displaying Adsense ads on many websites.
As Google officially says this happened due to a detection of invalid traffic on these sites:
Google is continually investing in measures to protect and improve the experience for our advertisers, publishers, and users.
As we launch improvements to our systems and defenses, sites with invalid traffic may experience limited ad-serving. Additionally, if we are unable to verify the quality of your traffic, we may limit or disable your ad serving.
Please check out our help center on Invalid Traffic to learn about how to prevent invalid traffic and improve your traffic quality.
Please have a look in the official Google support forum about this issue:
If you notice this issue on your own websites and ads stopped displaying from one moment to another it’s likely that your website is affected by this recent Google AdSense update.
To resolve it you need to make sure that you get better traffic and you also need to ensure that you increase the overall quality of your website which means you need to create more genuine content.
Also, follow all the Google AdSense terms and do not try to bend them:
It may take a lot of time until your ads will come back so you’ll need to be patient when this happened to your website.