200: OK. Returns the raw CSV formatted data. The header will have the content type of data. For example: content-type text/csv; charset=utf-8

401: Unauthorized. If the authentication failed is returned, either the username or password is incorrect. Verify the both from the applications Integrations / API Keys for your account in the application.
403: Access Denied. Access to the specified report is denied.
404: NotFound. If you get a not found error, the fileId is likely incorrect or that the file no longer exists to be downloaded. Verify you have a valid and correct fileId. The fileId needs to concatenate the ID + extension or you will receive this 404 error. So if the ID is 5538bf79de51e8633 and the ext is csv, the proper fileId is 5538bf79de51e8633.csv. This will return an error in XML so it is probably best to only look at the status code (404) and not an expected reply in JSON.