Function "onUserEarnedReward" is never used in admob

This issue is related to the google AdMob library i.e 20.1.0. There are many breaking changes coming in version 20.0.0 as it introduces many new APIs, deprecates many classes and APIs, and renaming many classes. Furthermore, you check out this link for complete migration.

Below is the sample code I've mentioned in both methods to get a callback of earned reward.