App open ad not working in unity, shows DefaultLifecycleObserver error in Android devices

[Ritwik Sinha]

Hi,
Please find the attached error in the image here, it shows Android.Java.Exception (Failed resolution of DefaultLifecycleObserver) for only App open ad when built for android device using unity. Works fine on unity editor though. What could be the reason?
The same error happens on android build for the sample unity project("HelloWorld") provided by google admob.

How to resolve this error, please let me know thanks.

[Ritwik Sinha]

I'm using unity 2022.3.28f1 with default java jdk and android sdk as provided by Unity, with no added configurations in proguard or gradle. Please help. The rest of the ads work only app open ads don't work.
The same happens with the sample unity project("HelloWorld") provided by google admob found here https://github.com/googleads/googleads-mobile-unity/tree/main/samples/HelloWorld.

Please let me know. Thanks.