Newbe setting up DS 923+ with the DSM version 7.2, first attempt to transfer files yıelds empty folders

I have many nested folders of photos. I am trying to move them into a shared folder rather than using Sinhala G photos because I like to do my own file management.

I am able to upload 20 photos at a time by choosing individual files. But when I choose the file folder that contains the very same 20 photos, I am not allowed to hit the upload button for that folder.

I have tried and receive the same result from my MacBook Pro and from my Windows laptop.

Please help