Additional information from testing I’ve done today.
I uploaded a new file and it has better results, but not great.
When I click “download” the file actually downloads to my PC, however the screen “busy” graphic in the theme is displayed and never goes away (The theme is the Salient Theme from Elegant Themes) and the download count is incremented by 2 – it goes from 0 to 2 to 4, etc.
The original file that I updated May 14, still does not download at all.
Do all files have to be re-uploaded every time the plugin is upgraded?