java.lang.NoClassDefFoundError: Failed resolution of: Lcom/Google/Android/gms/common/API/API$zzf;

I have also faced this issue while adding firebase auth in my project and issue was I have not added google auth as dependency in build.gradle. Adding below dependencies solved the problem

implementation 'com.google.android.gms:play-services-auth:16.0.0'
implementation 'com.google.firebase:firebase-auth:16.0.3'

I had this error due to dependency conflicts in Firebase. In particular, dependencies of the module Auth. In this case, updating the dependencies should solve the problem.