Windows vs. Mac
That's the way it has always worked - except for now on my Windows 11 PC. Platform make a difference? When I try to open anything on the site, I get a blank screen. When I try to open a page with an HTML editor on it, I get an error: "Please open a PHP document in order to use this interface" (the page is definitely a PHP page).
The site (see Private for the URL) and all of its pages work perfectly on my Mac and on the public server.