Delighted to say, buy pure chance, I found the problem and fixed it.
In the vimeo link, looking closely through all the steps, in minute 1:50 it shows the folder of the theme ‘enfold’, inside a folder called ‘wp-enfold’.
Only by misplacing the ‘enfold-child’ file and zip that i downloaded from the vimeo comment, i saw that i had 2 folders named ‘enfold’ (one inside the other) and no folder called wp-enfold. this is how i received it from Kriesi’s download – different from their (your :) own video tutorial.
I checked on my FTP and found that I did in fact upload the container ‘enfold’ folder rather than the actual theme ‘enfold’ folder. I deleted it and uploaded the correct folder, checked the ‘Appearance’ page in my admin site – and saw the child!!
I don’t know why kriesi changed the folder name since the video was created, but I think you should consider fixing one of the 2.