When saving to Google Drive, the SSO panel displays a request asking to ALLOW access to the selected Google Account's Drive files.
For some reason Google denies the request with the following message.
The issue has something to do with the app being considered less secure.
The solution is to add Starry Night Web via the Managed App category of Google Account Admin.
Security > API Controls > App Access Control > Apps > Configure new app
Search for the Starry Night Web Client ID: 885176390412-
Choose: Starry Night Web
Configure as above.
Now SSO will allow access to your Google Drive.