You're technically downloading the file from yourself, since you're the "server" in this situation.

My hunch is that there's a dependency issue since you're running on a Mac that's never been on the internet.

I'd recommend downloading the Google Chrome installer and running that on the Mac, then try opening the index.html file using chrome.

If you're already using the latest version of chrome and this isn't working, you may be having issues with javascript. Again, download the latest version of the java installer, and make sure the browser settings aren't blocking it from running.

As a last-ditch option, you could just use the private key instead of a password+keystore. If you want to password protect the private key, throw it into a keypass database. If you really want a keystore too, use the one generated by keepass to access the password database. Then you can have your keepass password+keystore to access the private key.