In the current state, Keeps API can only be used through domain-wide delegation, with service accounts or an OAuth client ID, only for enterprise apps.

You can reach the resource following this path Admin Console> API Controls> Security> Domain-wide Delegation

If you have more doubts on how to use or configure Domain-Wide delegation, you can follow this guide.

Cheers!

Reference: https://issuetracker.google.com/issues/210500028#comment4