You can the HTTP GET method with the /Extractions/ExtractedFiles endpoint to get a list of files.
The file type of the note files is "Note". Then, you can download the file by using the /Extractions/ExtractedFiles('<ExtractedFileId>')/$value endpoint with the HTTP GET Method.
Hello @Ashwin.Srinivas ,
Please see this previous discussion thread on Maintenance Notes.
Would additionally note, that some extraction request types carry Maintenance Notes and some do not, and this would be consistent with the availability of the notes for reports in DSS GUI interface.
Would suggest to also be sure, that on your DSS User Preferences, the option "Enable RIC Maintenance Reports" is enabled: