Recuva deep scan cannot find files that are found by Puran

[AmelioG]

HI,

I have a exFAT external HD where I want to remove some personal files.

Files were deleted in the past but still present on the disk as I can effectively recover the content of those files with Puran file recovery in deep scan. (not the filename but the content)

So I decided to run Recuva to find those file and then permanently overwrite with Recuva.

However Recuva in deep scan is unable to find those files. After running for a while he tells me at the end that he found several thousands of file but none is recoverable. 

To complete the picture, those files remains on the disk even if I do a wipe free space through ccleaner.

Any idea why Recuva cannot find those files and how to remove those files?

Thanks

Amelio