I've been working on an Android project recently which required me to implement Google Sign-In feature in one the activity using Firebase. There's this unusual problem that I'm facing:
Whenever I build the program on my Android phone the google sign-in works fine. Enabling me to sign in easily. (I commit my code to Github) Now when my mentor fetches the updated code from GitHub and builds the project on his phone, the Google Sign-In does not work i.e. he's unable to log in.
He gets the following error:
E/AuthUI: A sign-in error occurred.
com.firebase.ui.auth.FirebaseUiException: Code: 12500, message: 12500:
at com.firebase.ui.auth.data.remote.GoogleSignInHandler.onActivityResult(GoogleSignInHandler.java:109)
at com.firebase.ui.auth.ui.idp.SingleSignInActivity.onActivityResult(SingleSignInActivity.java:128)
at android.app.Activity.dispatchActivityResult(Activity.java:7317)
at android.app.ActivityThread.deliverResults(ActivityThread.java:4436)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4484)
at android.app.ActivityThread.-wrap19(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1743)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6753)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:482)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
However, when I send him the APK build on my system it works fine on his device.
What could be the possible reason for this and how do I solve this problem?