Here are instruction how to whitelist WhoKnows for your G Suite users.
1) Go to the G Suite Admin | Security | API Controls | Manage Third-Party App Access by going here https://admin.google.com/ac/owl/list?tab=apps. Then, click on the "Configure new app" link and select "OAuth App Name Or Client iD" option in the dropdown menu.
2) In the field for the App or Client ID, enter 23155866186-rb7nalabmfk0etk5ar6lenoofb10gk0m.apps.googleusercontent.com and press the Search button.
3) You'll see the WhoKnows app show up in the search results, then just click the Select link for it.
4) Select the Client ID again and press the Select button.
5) Then, select Trusted and click the Configure button and that's it!
Now, all of the users in your G Suite will be whitelisted to leverage WhoKnows.