To me it seems like the issue might be that the SHA1 key you ar using is from debug and not release. Try some jks tool to check the SHA on your jks file or try

cd android 

//to change to android directory and then

./gradlew signingreport

then try searching for your jks and get the SHA key.

Why don't you try this Article. It is a bit outdated but is great for getting basic overview. If it still doesn't work try adding a web client too in the Google Cloud Console.