I had same problem, i did read some posts and was able to get work done by following below steps
step 1) please goto https://console.firebase.google.com
step 2) if you already have project with that packagename ->go to overview ->click on menu icon where packagne name is written
step 3) select settings goto-> tab General-> there will be option called Add fingerprint
Step 4) then generate Signing-certificate fingerprint by writing below command in command prompt before that you should have keystore and its path
keytool -exportcert -keystore "D:\PlayStore_keystore\myproject.jks" -list -v
Step 5) after click on enter you will be asked for
Enter keystore password :
Enter password which you have used for creating keystore
step 6) in step 5 you have got SHA1 paste that in certificate fingerprint and save it
step 7) now download new google-services.json file (as it conatins new client id ,certificate_hash etc)
step 8) paste that google-services.json file in app folder in your android project.
step 9) You are good to go...
http://stackoverflow.com/questions/36999751/google-signin-not-working-in-release-mode-apk-android/42921691#42921691
step 1) please goto https://console.firebase.google.com
step 2) if you already have project with that packagename ->go to overview ->click on menu icon where packagne name is written
step 3) select settings goto-> tab General-> there will be option called Add fingerprint
Step 4) then generate Signing-certificate fingerprint by writing below command in command prompt before that you should have keystore and its path
keytool -exportcert -keystore "D:\PlayStore_keystore\myproject.jks" -list -v
Step 5) after click on enter you will be asked for
Enter keystore password :
Enter password which you have used for creating keystore
step 6) in step 5 you have got SHA1 paste that in certificate fingerprint and save it
step 7) now download new google-services.json file (as it conatins new client id ,certificate_hash etc)
step 8) paste that google-services.json file in app folder in your android project.
step 9) You are good to go...
http://stackoverflow.com/questions/36999751/google-signin-not-working-in-release-mode-apk-android/42921691#42921691
