http Not Found CFN #0005 on https URL

Sorry for the slow reply. Are you still facing this problem or have you resolved this?

This would not be related to recent WP upgrades. Changing your site and WP URL settings will affect access to WP content, but does not impact static .html files like testfile.html. WP does not even enter into the picture.

Why would you still want to use HTTP anyway? The only difference with HTTPS is how the data is transmitted over the Internet. Everything else is the same.