Zzef error when building my game?

Been trying to fix this bug for a few days now.

I built my apk but I cant seem to even enter the game. In android studio it spits out this error which I do not understand.

12-12 10:38:59.743 21242-21242/com.TrisAviorEntertainment.WarOfTheOrigin E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.TrisAviorEntertainment.WarOfTheOrigin, PID: 21242
java.lang.NoClassDefFoundError: com.google.firebase.auth.api.internal.zzef
at com.google.firebase.auth.api.internal.zzeg.zzdk(Unknown Source)
at com.google.firebase.auth.FirebaseAuth.<init>(Unknown Source)
at com.google.firebase.auth.internal.zzj.<init>(Unknown Source)
at com.google.firebase.auth.zzp.create(Unknown Source)
at com.google.firebase.components.Lazy.lambda$new$0(com.google.firebase:firebase-common@@16.0.4:43)
at com.google.firebase.components.Lazy$$Lambda$1.get(com.google.firebase:firebase-common@@16.0.4)
at com.google.firebase.components.Lazy.get(com.google.firebase:firebase-common@@16.0.4:54)
at com.google.firebase.components.AbstractComponentContainer.get(com.google.firebase:firebase-common@@16.0.4:26)
at com.google.firebase.components.ComponentRuntime.get(com.google.firebase:firebase-common@@16.0.4:34)
at com.google.firebase.components.ComponentRuntime.initializeEagerComponents(com.google.firebase:firebase-common@@16.0.4:82)
at com.google.firebase.FirebaseApp.initializeAllApis(com.google.firebase:firebase-common@@16.0.4:761)
at com.google.firebase.FirebaseApp.initializeApp(com.google.firebase:firebase-common@@16.0.4:359)
at com.google.firebase.FirebaseApp.initializeApp(com.google.firebase:firebase-common@@16.0.4:324)
at com.google.firebase.FirebaseApp.initializeApp(com.google.firebase:firebase-common@@16.0.4:310)
at com.google.firebase.provider.FirebaseInitProvider.onCreate(com.google.firebase:firebase-common@@16.0.4:53)
at android.content.ContentProvider.attachInfo(ContentProvider.java:1716)
at android.content.ContentProvider.attachInfo(ContentProvider.java:1685)
at com.google.firebase.provider.FirebaseInitProvider.attachInfo(com.google.firebase:firebase-common@@16.0.4:47)
at android.app.ActivityThread.installProvider(ActivityThread.java:5555)
at android.app.ActivityThread.installContentProviders(ActivityThread.java:5150)
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5090)
at android.app.ActivityThread.access$1600(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1509)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5938)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1389)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)