550 Directory not empty

Hi everybody,

I downloaded SmartFTP because on the website was written we can delete even non empty folders.

I have a folder in the root of my FTP, inside I have many subfolder. All is empty. I already checked with many software, no .htaccess file no other hidden files, just empty folder as i can see.

I can change permission, i can rename it all of them, i can create new files in, but I cannot delete.

The error is 550 Directory not empty.

Is somebody have a solution for this please?