Admob native ads with xamarin: 'Ad failed to load : 0' - xamarin

Question

This issue only occurs with my implementation of native ads. Banner ads work fine. I adapted the custom renderers from this blog to work with native ads. I used test ad unit IDs.
Here is my custom renderer for Android:
[assembly: ExportRenderer(typeof(NativeAdView), typeof(NativeRendererAndroid))]
namespace XXX.Droid
{
public class NativeRendererAndroid : ViewRenderer<NativeAdView, AdView>
{
public NativeRendererAndroid(Context context) : base(context) { }
protected override void OnElementChanged(ElementChangedEventArgs<NativeAdView> e)
{
base.OnElementChanged(e);
if (e.NewElement != null && Control == null)
SetNativeControl(CreateAdView());
}
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == nameof(AdView.AdUnitId))
Control.AdUnitId = Element.AdUnitId;
}
private AdView CreateAdView()
{
var adView = new AdView(Context)
{
AdSize = new AdSize(AdSize.FullWidth, AdSize.AutoHeight),
AdUnitId = Element.AdUnitId
};
adView.LayoutParameters = new LinearLayout.LayoutParams(LayoutParams.MatchParent, LayoutParams.MatchParent);
adView.LoadAd(new AdRequest.Builder().Build());
return adView;
}
}
}
And for iOS:
[assembly: ExportRenderer(typeof(NativeAdView), typeof(NativeRendereriOS))]
namespace XXX.iOS
{
public class NativeRendereriOS : ViewRenderer<NativeAdView, NativeExpressAdView>
{
protected override void OnElementChanged(ElementChangedEventArgs<NativeAdView> e)
{
base.OnElementChanged(e);
if (Control == null)
{
SetNativeControl(CreateNativeAd());
}
}
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == nameof(NativeExpressAdView.AdUnitID))
Control.AdUnitID = Element.AdUnitId;
}
private NativeExpressAdView CreateNativeAd()
{
AdSize adSize = new AdSize();
adSize.Size = new CGSize(UIScreen.MainScreen.Bounds.Size.Width, 49);
var nativeAd = new NativeExpressAdView(adSize)
{
AdUnitID = Element.AdUnitId,
RootViewController = GetVisibleViewController()
};
nativeAd.LoadRequest(GetRequest());
Request GetRequest()
{
var request = Request.GetDefaultRequest();
return request;
}
return nativeAd;
}
private UIViewController GetVisibleViewController()
{
var windows = UIApplication.SharedApplication.Windows;
foreach (var window in windows)
{
if (window.RootViewController != null)
{
return window.RootViewController;
}
}
return null;
}
}
}
These custom renderers are very similar to the ones linked in the blog above. Perhaps there is something I need to include for native ads that is not used for banner ads?
Once I get the ad loading correctly, I would like to put it in a ListView, but for now I just have it as a View.
Edit: For clarification, when using the above custom renderers, everything builds successfully, but when the ad tries to load, 'Ad failed to load : 0' gets printed in the debug and the NativeAdView remains transparent. This is both both platforms.