My blog feed site is getting only Public Service ads to be displayed under each post.. why Not Commercial ads???
Sometimes it happens when Adsense crawler does not understand the content of website to show relevant ads.
There have so many reason for run public service ads. 1. If you are not verify your account (Not enter generated PIN) 2. If you are not still getting approval from adsense(For blog) 3. If adsense have not any available ads for show your blog. & many more...
Is adsense showing properly on other websites? -if no, you might have an account problem like account verification -check Adsense Setup > Allowed Sites. Do you have that enabled, and if so is your domain added? Your site with psa ads, do you have a topic or use words that google doesn't like: ex, adult related, death, guns, etc?