On accessing Extranet URL from Internet, we got this message:
You are not authorized to access this site.
The application you are attempting to access requires additional authorization. If you feel you have received this message in error, please contact your local business Help Desk.
This error is coming because we have SSO enabled our Extranet also. If the user exists in the SSO database and doesn't exist in the FND_USER table of Oracle E-Business Suite, this error would appear.
After creating the users locally in E-Business Suite, this error should disappear.