Sorry, I was unable to reproduce this issue at my end. I used the same URI with Google Drive storage and sub-folders. Following were the parameters I passed.
Please share your complete code including correct folder names. You can copy your code in a text file and follow http://www.aspose.com/corporate/purchase/faqs/send-license-to-aspose-staff.aspx to send that text file to me.
When I delete a folder from Google Drive storage, it also deletes all sub-folders. How can you access sub-folder after deleting main folder? However, if you have deleted ee folder and ff folder is still there, you should pass &folder=ff in that case.
You can also follow http://www.aspose.com/docs/display/rest/Get+a+List+of+all+Files+and+Subfolders to get a list of files and folders. This will give you the idea what folder structure exists on your storage. If you still find any issue, you can share your App SID and Key by following http://www.aspose.com/corporate/purchase/faqs/send-license-to-aspose-staff.aspx.