How to clear configuration?

We set up a test configuration with one Gmail account, now we need to clear it and set up another (the client’s) – how do we get away from the “Postman is configured.” screen? We’ve gone in and deleted the client ID and project from the initial Gmail setup, and I deleted the only database rows I could find in wp_options that looked related to Postman, but it’s still showing up as configured. Help?