"This app is not authorized to use Firebase Authentication" in Emulator

In order to prevent abuse the firebase phone authentication wont work in emulator.

But if you want it for testing purpose then you should add use some testing phone number in firebase console that will work in emulator.

Go to your firebase console -> Authentication -> SIGN-IN Method -> Phone and check the "Phone numbers for testing (optional)" field.

sha1 generation in android studio:

Select Gradle in android studio from right panel

Select Your App

In tasks -> android-> signingReport

Double click signingReport.

You will find the sha1 fingerprint in the "Gradle Console"

add this sha1 fingerprint in firebase console