Firebase Authentication not working when publish app to Google Play Console

I have an app that contains Google sign-in functionality and am using Firebase Authentication to do that.

Everything works perfectly when building directly to the device. However, after exporting the aab file and uploading it to Google Play Console for publishing, I tried downloading the signed apk file to install and realized that this login function did not work.

I wonder if anyone is having the same problem as me?

After many days of research, I realized what I encountered:

1. Add SHA-1 and SHA-256 of App signing key certificate and Upload key certificate to Firebase. (Many people have probably seen this suggestion on many easily searchable answers)
2. REMEMBER "Link Cloud project" at Google Play Console > App Integrity > Play Integrity API. Select the firebase project you created and add SHA in step 1 above then submit.

Everything works like a charm. xD