Solution 1 :
After spending 2days with these problem i came to know that there is three different signing keys.
1- The debug key
2- The release key
3- Google Play App signing key
After entering these three different keys in my firebase account resolved my issue. For more info refer this answer https://stackoverflow.com/a/62231264/12595949
why do i get problems in signing in through google using firebase. when i try to run the app through android studio my app sign in perfectly but when i upload the apk to playstore it doesnt sign in and gives an error code :10. Is there anything to do with SHA 1? does the SHA 1 differs between debug apk and release apk?