Select you firebase project
Select Authentication -> Sign-In method
Enable Google Login
Select Project Settings
Select Your app and add SHA-1 and SHA-256 key which you had created when generating google-service.json file
After you have added keys again download google-service.json file and replace it in your android code
Open CMD and select path to bin folder of JAVA -> C:\Program Files\Java\jdk1.8.0.40\bin
Copy your keystore to root of your drive eg:- D:\keystore_name.jks
Copy and Paste keytool -list -v -keystore D:\keystore_name.jks -alias alias_name
Enter keystore password (password might be not visible)
Copy SHA1 and SHA256 key and add in firebase as shown above
After you have added keys again download google-service.json file and replace it in your android code
Select OPT-OUT or if you select continue then you have upload keystore and get SHA-1 key from google app signing certificate as follows
Navigate to the Google Play Console and login
Choose the application you are signing
Go to Release Management –> App Signing
Copy /Download the SHA-1 or SHA-256 certificate fingerprint from the App signing certificate section
After you have added keys again download google-service.json file and replace it in your android code
