Apple iAd working in Germany / Russia but not in Netherlands?
In this screenshot you can see that my iAd advertisements have a very low fill rate. In Netherlands it's terrible. How is that possible? What can I do to improve it? Is it even worth it because it looks like people don't like my app?
There is nothing you can do about the availability of iAd advertisements based on specific countries. Advertisers have to include the Netherlands in their list of targeted regions for iAd advertisements to appear in the Netherlands. Apparently the Netherlands isn't a very large market for iAd advertisers, the fill rate on one of my more popular applications is only 5% in the Netherlands. In addition, iAd is not supported globally. You can see a list of supported countries here.
You should consider using another ad network, AdMob is a popular one, when an iAd advertisement fails to be filled.