Scenario
You are an admin on PlusPlus. Your company uses Google Workspace and you wish to allow users in your organization to access their Google Drive from PlusPlus - e.g. to import codelabs directly from Google Docs.
Solution
Ask your Google Workspace admins to approve the PlusPlus App, if it's not been approved already.
Head over to Settings ⇒ Integrations ⇒ Storage ⇒ Google Drive
Toggle on Enable Google Drive integration
Click on Save
Go deeper
Enabling Google Drive integration just allows users to attempt to access Google Drive from PlusPlus (e.g. on Codelab import dialog). When they request this for the first time, they'll be asked to authorize PlusPlus to gain read-only access to their documents.
Furthermore, if your users get "Authorization Error 400: redirect_uri_mismatch", that means that your PlusPlus domain has not yet been configured on our end. Please reach out to Support to have that be enabled.