This is what google says “It could be that you have only recently created a new Ad Unit ID and requesting for live ads. It could take a few hours for ads to start getting served if that is that case. If you are receiving test ads then your implementation is fine. Just wait a … Read more
Some Background When Unity builds your project for Android, it invokes several tools from the Android SDK. As part of that process, it converts all of your native (Java) code for Android into a file format called DEX (Dalvik executable). All of your Android plugins get built up into a single package using that tool. … Read more
Until Admob fixes this issue as Oush pointed out, you can just delete the notification channel right after it was crated by admob, so it won’t confuse your users: