Before the upgrade it's working fine, after upgrade, my user experienced that error:
External table is not in the expected format.
After debugging, found out that there's 2 files being processed, even though my user only puts 1 file into the upload folder.
Turned out to be the second file is Thumbs.db, usually used for thumbnails.
But I cannot see this file in the folder itself.
So what do we need to do?
Simple, just ask your user to go to Windows Explorer, go to Tools, Folder Options
On View tab, tick the first one, Always show icons, never thumbnails then click ok.
Go to that upload folder, remove any Thumbs.db if there's is any.
It should solve the problem.
Reference: here
