I’m facing the same troubles, but in my own clone of OAuth2 (OpenId) for my distributed backend sessions system…
The settings are defined on DefaultEngine.ini (or somewhere appropiate)
[OnlineSubsystem]
DefaultPlatformService=Google
[OnlineSubsystemGoogle]
ClientId=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
ClientSecret=yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
[OnlineSubsystemGoogle.OnlineIdentityGoogle]
RedirectPort=xxxx
LoginRedirectUrl=http://localhost:xxxx/callback
but i can’t get it work either…
seems some documentation, missing… or it’s missing the http loopback listener… 