My Cloud Home Duo syncs only folders, not files in them

I sync a folder by right clicking and selecting Sync to “*****'d My Cloud Home Duo (Z)”; whereupon it saves that folder to the ‘Sync from desktop’ folder on my My Cloud Duo and it also saves all the sub-folders in it, but none of the files in the main folder nor in any of the sub-folders is saved.
QUOTE from manual: Any content added or modified to this folder will automatically sync to the My Cloud Home device . . ., this does not happen: files do not appear, neither do any new folders appear which are generated after the initial sync.
It appears that there is only partial functionality.
Any ideas anyone, bearing in mind that I am a septuagenarian and not a 20-year-old whizz-kid.

The following article may help