Fixing Google Sign-In Error 12500 on Android

Post author: Nanfeng
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Background

A production app that had been stable for a long time suddenly received many reports that Google Sign-In no longer worked. The app had not been updated recently, so the failure was unexpected.

Error log

Testing on my own phone produced:

1 2	signInResult:failed code=com.google.android.gms.common.api.ApiException: 12500: ApiException{"code":-1,"err":"Login failed (12500)"}

I used the error log to investigate the common causes:

Resolution

After verifying all likely configuration problems, I found nothing incorrect in the app. I re-entered the SHA-1 fingerprint in Google Cloud Console, saved the configuration, and refreshed it. Google Sign-In then worked again.

My personal conclusion was that the platform configuration had become inconsistent. Only this one app was affected; the other apps continued working normally.