I think this is related to the site redesign earlier in the year …
The Classic has buttons to check the latest versions of the Engine and Web Interface codebases - but currently it 404s. I can see it’s requesting this URL: http://hestiapi.com/upgrade/engine/check-0.1.2.htm
Obviously the legacy site is now on /old/ so you might want to add a redirect from /upgrade to /old/upgrade? I know further updates to the Classic codebase are unlikely, but it may happen 