1000 page impressions but no earnings
Some webmasters are confused about how Google pays them.
The AdSense program is working in two ways: one that can pay you when someone clicks on the ads displayed on your site or at page impressions.
It is possible to make 1000 page impressions but $0. The reason is that the ads displayed on you site are not paid by the advertisers at page impressions. This ads are paied at click “CPC”.
So if you make 1000 page impressions and didn’t received any click or the ads were not even paid in the CPM system you don’t make any money.
This is a problem that you can’t control because Google automatically display whichever ad or ads representing the highest revenue potential for you, whether they’re CPC or CPM ads.
If you see that your ads are not performing well try to make some tests with diferent positions and colors on site. I am sure you will find in time a good position and shape for your ads.