NEVER MIND!

The solution was presented in that exchange, but it wasn't clear to Scully then or to me when I read it. But now that I've re-read the entire exchange again, the answer is to go to the COWOA Admin and turn to 'false' the option "Enable Forced Logoff".

When I setup the module, I assumed that making that option 'true' would allow the user the option to log off after completing his or her checkout. I didn't get that it would automatically log the user off AND disable access to any and all downloadable file links.

A person selling downloads in Zen Cart MUST HAVE the the COWOA Admin option "Enable Forced Logoff" set to 'false' -- or else the customer has no opportunity to download their purchase, ever!