to access the file you need the service account to have acces to the file you can do it by

Find your service account email from your JSON credentials file - it looks like: [email protected]

Open your Google Doc in the browser

Click the "Share" button in the top right

Add the service account email as an editor/viewer

Make sure to check these settings:

"Notify people" should be unchecked Click "Send" or "Share" to confirm

hopes it work