Ads not showing in single post

Hi.
Thank you very much for this very useful plugin.
I’v installed it in one of my websites, but I don’t know why ads are not displayed on single post (they are displayed on home page, category archive and single pages).
Can you help me plz?
My website link (It’s in arabic, you can see the ad in the header as example):

http://www.ouazzaneyes.com/

http://wordpress.org/extend/plugins/simple-ads-manager/