External HDD visable but suddenly gone unreadable

Using Testdisk 7.0 I am getting the same screen as before

That would mean that both 7.0 and 7.1 see your single partition but only find the root directories/files in DOS. There are no data files in that partition. In mfx's case TestDisk straightaway showed his files and he was able to copy all to the destination disk.

So does that mean my files are not recoverable?

Not by any other means that I know of, because with no other software you can change the sector size to 4096 and ask it to read the drive.

At this point however, I remember that atleast one user had reported that while he was unable to retrieve any data with TestDisk running on Windows, using it on Linux worked. He used System Rescue CD - which is Linux based and ran the Linux version of TestDisk in it. SystemRescueCd - System Rescue Cd Homepage . ( You have to make a bootable CD or Flash drive, boot from it and run TestDisk. The process will be the same. )

If you have a friend who is a Linux Guru, you can ask him to run the linux version of TestDisk as aforesaid and try.