iPhone iAds Not working on iPhone 4

I have an iPhone app in the app store, but I am having a problem with iAds. iAds are showing up as they should on iPhone 3G and iPhone 3GS phones that have downloaded the app, but the iAds are not showing up on any开发者_如何转开发 iPhone 4 phones. They are all running the latest software version (iOS 4.2.1). Also, both iPhone 4 and iPhone 3GS phones were both correctly displaying test iAds during my testing phase. Does anyone know what might be causing this issue? Thanks in advance.

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The iAds service currently has a really low fill rate (ie, you won't receive an advert every time you request one and, particularly outside the US, are often quite a bit more likely not to receive one). Quite probably either what you're seeing is a coincidence or the particular ads that Apple happens to be running at the minute in your territory aren't being supplied for the iPhone 4 with your app's combination of other ad-relevant metadata (and exactly what Apple use is undisclosed, just assume all the information you supply about your app may be relevant when picking which adverts to serve).

If your app showed the test iAds correctly then it'll show proper iAds correctly. Since Apple require that you properly implement showing/hiding of the iAd bar based on whether you receive an advert, it's safe to assume that they test this feature of your app.