No virtual method verifyPhoneNumber, FATAL EXCEPTION: main

implementation platform('com.google.firebase:firebase-bom:26.1.0')
    implementation 'com.google.firebase:firebase-auth'
    implementation 'com.firebaseui:firebase-ui-auth:7.0.0'

this is the real correction ;)

you just need to update firebaseUI to the latest version

implementation 'com.firebaseui:firebase-ui-auth:7.1.0' //or higher

it means if you use the latest firebase you need to use the latest firebaseUI as mentioned here https://github.com/firebase/FirebaseUI-Android/issues/1868

Today, i had the same problem when i used the latest version of the Firebase Auth -'com.google.firebase:firebase-auth:20.0.0'. Then again i changed it to previous working version ('com.google.firebase:firebase-auth:19.4.0') and it started working again. Hope this is what you are looking for

I managed to resolve by downgrading firebase auth, and firebase auth-ui to:

implementation 'com.google.firebase:firebase-auth:19.3.1'
implementation 'com.firebaseui:firebase-ui-auth:6.2.0'

then I removed:

// Firebase
implementation platform('com.google.firebase:firebase-bom:26.0.0')

So the gradle now looks like:

// Firebase
//Firebase Authentication
implementation 'com.google.firebase:firebase-auth:19.3.1'
implementation 'com.firebaseui:firebase-ui-auth:6.2.0'

//Firebase Database
implementation 'com.google.firebase:firebase-database:19.5.1'
// FirebaseUI for Firebase Realtime Database
implementation 'com.firebaseui:firebase-ui-database:6.4.0'

//Firebase Messaging
implementation 'com.google.firebase:firebase-messaging:21.0.0'

//Firebase Storage
implementation 'com.google.firebase:firebase-storage:19.2.0'

implementation 'com.google.firebase:firebase-perf:19.0.9'

implementation 'com.google.firebase:firebase-analytics:18.0.0'
//////////////////////////////////////////////////////////////////////

Somehow firebase performance is conflicting with firebase authentication. Everything now works as it should