First make sure you have signed up to adsense and put your tracking code in your hubpages account under the "affiliate settings" section.....
It depends on how many views you have had. Click rates are 2% or less and hubpages take 40% of impressions.
This means that you will probably only average one click per 100 views.
Also it depends on where your traffic comes from. If it is internal hubpages traffic, remember that hubbers don't click. You need 100 search engine views on average to get a click.
Search the forum for tips on getting organic traffic.
You can also maximise your hubs potential by using multiple text boxes rather than putting all of your content in one. Add some pictures and video as well.
The forum is a great place to learn.