Hello,
I’m using UE 5.1.1 and I have configured all the Android section, I’ve trying to get the google login UI, it never shown even with multiple account on the device, also the login alway fail. I managed to success a login the first time, but after restarting the game on the device it failed since. And since login fail, I can’t test in app purshase 
The account is added a test account in google internal test setting and in google console OAuth consent screen
also i have activated API
This is the error
[420]LogOnline: OSS: GPG OnAuthActionFinished: SIGN IN, AuthStatus: ERROR_NOT_AUTHORIZED
[420]LogOnline: OSS: OnAuthActionFinished SIGN IN -3
[420]LogOnline: OSS: FOnlineAsyncTaskGooglePlayShowLoginUI::OnAuthActionFinished 1 -3
[420]LogOnline: Warning: OSS: FOnlineAsyncTaskGooglePlayShowLoginUI::Authorized 0
[420]LogOnline: OSS: FOnlineAsyncTaskGooglePlayShowLoginUI Failure
[421]LogOnline: Warning: OSS: Async task ‘ShowLoginUI’ failed in 6.349396 seconds
[421]LogOnline: OSS: FOnlineAsyncTaskGooglePlayShowLoginUI: Finalize.
[421]LogOnline: OSS: FOnlineAsyncTaskGooglePlayShowLoginUI: TriggerDelegates Success: 0.