Prime[31] Windows Phone Admob issue

issue.cs

public void ShowBanner()
{
    // DOES NOT SHOW IMPRESSIONS
    WinPhoneAdMob.createBanner("ca-app-pub-xxxxxx", AdFormat.SmartBanner, AdHorizontalAlignment.Center, AdVerticalAlignment.Bottom, false);

    // SHOWS IMPRESSIONS
    WinPhoneAdMob.createBanner("ca-app-pub-xxxxxx", AdFormat.Banner, AdHorizontalAlignment.Center, AdVerticalAlignment.Bottom, true);
}