Overdrive needs access to Google Drive to display folders and files. If you see a message that the G Suite administrator for your domain has disabled 3rd party Drive Apps you will need to re-enable them as follows.
As the G Suite domain administrator:
- Access the G Suite cpanel
- Go to Apps > G Suite > Drive & Docs > Data Access
- Check the box "Allow users to access Google Drive with the Drive SDK API"
- Save the settings.
When you log back in to Overdrive the message should have gone and you will see any folders within the root folder you have chosen.