The error Ad failed to load: 3 means no ad fill, not a coding issue. The adaptive test ad unit /21775744923/example/adaptive-banner often doesn’t serve ads. To test adaptive banners, use Google’s universal AdMob test ID (ca-app-pub-3940256099942544/9214589741) or create your own ad unit in Google Ad Manager with active line items. Also ensure you calculate adaptive size dynamically using AdSize.getCurrentOrientationAnchoredAdaptiveBannerAdSize() and set your test device ID before loading the ad.