A few months ago, I faced this problem and figured it out. I would like to share my experience so it might help you. See following steps to figure this issue.
1. Make sure you are strictly following Google adsense program policies and didn’t get any mail about blocking from adsense.
2. Make sure you don’t have adblock installed or no block for adsense in server firewall/ security suit.
3. First test in another browser(chrome/firefox/IE) and see whether it’s working. It would be better if you could test on another PC.
4. Check adsense sandbox for your site and see whether it shows ads.
5. If you have not received first payment and earnings have reached $10, Google sends PIN number for verification process. Make sure, you have verified PIN number. If no, wait for PIN or request it again from your adsense account.
6. If you are using wordpress/Joomla..etc CMS. It might be due to configuration. So create a test HTML page and put adsense code, upload it independent from CMS and see whether it works.
8. Use Adsense Troubleshooter
Blank ads only on few pages:
If ads aren’t showing on specific pages, there is a problem with that individual page. The most common reasons for ads not showing are a lack of text (don’t count images and videos) or the use of stop words (all the common swear words plus others they have decided aren’t family safe).
It’s also possible that there are no advertisers for the keywords in your page’s content. Either you get them PSAs (Public Service Ads) or a blank ad block. To remedy this, you could use alternative ads in place of the blank spots. See here for specifying alternate ads.
Hope, It helps. Share your opinion to fix this issue.