Google AdSense is now warning some publishers that their earnings are at risk because they have not uploaded an ads.txt file to the site's root domain. Google says "To prevent severe impact on revenue, download an ads.txt file then upload the file to the root level domain of each site."
You may see a warning at the top of your Google AdSense console that says "Earnings at risk - You need to fix some ads.txt file issues to avoid severe impact to your revenue." Then two action buttons, one to "Fix Now" and the other to "Learn More."
Here is a screen shot (click to enlarge):
Then when you click on it, it shows you this warning that reads "To prevent severe impact on revenue, download an ads.txt file then upload the file to the root level domain of each site." "It may take a few days for changes to update. If you’re using another ad network, remember to add the network to the ads.txt file. See the ads.txt guide for more details," Google added:
Here is a screen shot (click to enlarge):
I barely use any AdSense on this site, so I am not worried but someone who depends on AdSense for income, this can be a scary thing.
Forum discussion at WebmasterWorld.
