Interstitial / Fullscreen Ads Suddenly Stopped Working

My interstitial ads stopped working on two of my apps. The fill rate is 84.07%. However, it is working on my other apps. The way I display fullscreen ads are just the same on all apps. I am not updating the apps yet so I wonder why it stopped working on those two apps. This happened after adding Rewarded Videos only on AdMob. I havent modified anything on the codes yet. Its weird because it is still working in my other apps. All my banner ads are working properly. I even posted this on a forum but no answer yet. TIA.!msg/google-admob-help-forum/m3pIMs0zkCk/kdSzW2quBQAJ

All ads on all apps work fine using my brother’s phone. However, fullscreen ads fail to load only on my phone and my tablet. My brother and I have the same network. I am not modifying my phone settings and I even reformatted my tablet then installed all those apps again but still it fails to load. Really weird. Has anyone experienced this too?