Looks like the issues was with the visibility of the files and folders in Google Drive. As said before the code is good all things pointed to something up with Google Drive.
To make the files and folders visible again I did the following;
- From within drive.google.com select the the files/folders in question
- From the 'More' button choose 'Share'
- Change the 'Who has Access' settings, click 'Save' then 'Done'
- Revert 'Who has Access' to previous setting if required.
So the visibility on certain folders is being lost or corrupted somehow.
UPDATE
I wrote a Google Apps Script that updates the permissions of the sub folders and call it from my web app. The script need to created as Web App and deployed for use. THe script is called via regular script src (as XHR isn't allowed with Google Apps Scripts)
function doGet(request) {
var folders = DriveApp.getRootFolder().getFoldersByName(request.parameters.folder);
while (folders.hasNext()) {
var folder = folders.next();
var subFolders = folder.getFolders();
while (subFolders.hasNext()) {
var subFolder = subFolders.next();
subFolder.setSharing(DriveApp.Access.DOMAIN_WITH_LINK, DriveApp.Permission.VIEW );
}
}
var result = '';
return ContentService.createTextOutput(result).setMimeType(ContentService.MimeType.JAVASCRIPT);
}
Hope this is of some help to someone.