Full Error Message: 
Error while creating new document. Error message: Error: 401. Error description: { “error”: { “errors”: [ { “domain”: “global”, “reason”: “authError”, “message”: “Invalid Credentials”, “locationType”: “header”, “location”: “Authorization” } ], “code”: 401, “message”: “Invalid Credentials” } }

-You may get this error message if you do not have proper credentials or permission to the google doc template or the folder it is being stored in.

How to resolve:
-Make sure the user trying to generate document has authorized their own google drive under RS Documents Configuration tab.
-Check user access to google doc template and to google drive that is being used. Need to have edit or full access to the folder in order to generate documents there.