Crash Application when implement mediation

[onstonboy]

Hi, currently i want to implement admob mediation with uniti ads into my application. When i try to implement

implementation 'com.unity3d.ads:unity-ads:4.0.0'
implementation 'com.google.ads.mediation:unity:4.0.0.0'

Then run application, it will be crashed cause:
java.lang.NoClassDefFoundError: Failed resolution of: Lcom/google/android/gms/ads/reward/RewardedVideoAdListener;

Caused by: java.lang.ClassNotFoundException: Didn't find class "com.google.android.gms.ads.reward.RewardedVideoAdListener" on path...

Please help!!