Full Error Message:
Error while creating new document. Error message: Application unauthorized.
Please authorize before trying to access Google Drive.

-You may get this error message when trying to generate a document though your google drive has not  been connected and app unauthorized.

How to resolve: 
You need to do first step in documentation which is to go to “RS Documents Configuration” tab (can access from RS Documents app window or by clicking the + sign for more tabs) and click “Grant access.” Then you will follow the steps to connect your google drive account you would like to use to generate documents.
NOTE: If you receive an error message when authorizing your Google Drive which refers to”Error: redirect_uri_mismatch” with custom domain, please go to AppExchange to upgrade your app package version to latest available. After you upgrade your package version, then proceed back to RS Documents Configuration tab to authorize app with your chosen google drive account.