It's impossible for me to offer any ideas as to why the download function would "stop dead" on anyone's machine, particularly before commencing.
If I paste the URL in on Firefox, Chrome, or Edge I instantly get a Save dialog for the download. The URL manipulation I use to force immediate download has been the same for years now, the only thing that changes is the file identifier.
Brian - Windows 10 Home, 64-Bit, Version 1809, Build 17763
Explanations exist; they have existed for all time; there is always a well-known solution to every human problem — neat, plausible, and wrong.
~ H.L. Mencken, AKA The Sage of Baltimore