I've implemented your control, but I'm only getting the default AdDuplex ad. What am I doing wrong?

Provided that there are no connectivity problems there are a couple of things that can cause that:

• AdDuplex control is obstructed by some other element on your page. Make sure nothing covers (in full or partially) the AdDuplex control when it becomes visible.
• You have a startup animation that renders the control invisible (or obstructed) on launch. Make AdDuplex control collapsed on launch and only set it to be visible when your startup animation is completed.
• You have no ID_CAP_NETWORKING capability specified in your app's manifest. Add <Capability Name="ID_CAP_NETWORKING" /> to your WMAppManifest.xml