[Plugin: Advertising Manager] Doesn't display ad

I have been trying to show Google AdSense Ads through Advertising Manager and have had nothing but trouble. I configured it correctly and everything appears to be going fine, but when I get to the blog itself, no ad shows up. The widget blocks off appropriate space, but doesn’t show the ad. I am trying to use the widget and have looked at ALL the settings and can’t get it to work. I can see google ads with the option of displaying ads after posts my theme provides, but I want ads in my column as a widget.