Below code I am using for Google login.I added google-services.json file in the app folder.I am using classpath \'com.google.gms:google-services:2.0.0
It's likely that your issue is in that you picked the SHA1 from the ~/.android/debug.keystore, but not using it to sign your build.
Go to the module options Signing tab and add a profile with the only field Store File set to /Users/
On the Flavors tab pick it in the Signing Config drop-down.
On the Build Types tab pick it in the Signing Config drop-down for your build type (likely to be Debug).
Cleanup and rebuild.