i create the trial looker instance on gcp. Console.
How to access the admin page for looker.
There is only instance information on gcp looker.
i resolved this by myself.
https://cloud.google.com/looker/docs/looker-core-create-oauth
in APIs & Services > Credentials > Authorized redirect URIs section
add "https://<your own uuid>.looker.app/oauth2callback"
i shoud read this carefully....