There are many reasons behind not displaying of the adsense ads inside your blogger. Few of the most common reasons are -
1. Google detecting same IP making multiple requests of ads in short time. This is fail-safe for both the adsense account owner and google's way of protecting advertisers money. They just stop showing ad on same website from same IP if accessed more than once on same page-view.
2. Inorganic traffic source detection. If the google adsense
has found too many inorganic traffic source. for example, PTC sites traffic. In such case google stops displaying the ads on the website. Also deducts the money during the payout under the option of "Invalid traffic
3. Browser Adblockers. With opera and Firefox making their browsers enabled with adblocker by default, it becomes harder to see ads on the website. You have to disable them on your browser to view the ads.
4. Google Smartpricing. In such case the amount of ads on your blog gets reduced. This happens when your website sends low quality clicks and readers to the advertisers. In such case advertiser algorithm filters your site from displaying ads on it. This rarely happens for new sites but old and established site has higher chance of getting smartpriced.
5. Using ad components more than the specified amount by adsense. Google has restriction for number of ads being allowed on the website. So you have to follow that number in order to get compliance for the ads display. Make sure you are not using excessive ad slots and reducing them could show the ads back again.
6. Please do verify that google has not disabled your ad for click bombing or any other activity. And in such case you get an email for such activity so do check the associated email as well.
If you check all of the above mentioned reasons and didn't find any valid reason for the ad display then I suggest contacting google support. They can guide you on why the ads are not being displayed.