I think that’s because you’re missing one dependency:
implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"
Get the latest version of lifecycle-common-java8 here
See the documentation:
If you use Java 8 Language, then observe events with
DefaultLifecycleObserver. To include it you should add
“androidx.lifecycle:lifecycle-common-java8:” to your
build.gradle file.