Mystery IP cache problem one macbook all accounts all browsers


Sister has a macbook running 10.15.6 Catalina used to manage a WordPress site on a virtual hosting service. As of a few days ago, the macbook fails to access the site and gets a "this site's IP has been changed" message. Phone and tablet on her same home network can access the site fine. I (on a different continent) can access the site fine. Nslookup for the site on her macbook gives the same result as it does for me. Hosting provider insists it's an IP cache issue on her machine.

Things she has already tried:

  • sudo killall -HUP mDNSResponder
  • DNS set to GoogleDNS
  • Safari, Firefox, and Chrome, all same issue
  • New user account on Macbook, Safari, same issue
  • Safari History->Clear History
  • Safari Preferences->Privacy->Manage Website Data->Clear All
  • Safari Develop->Empty Caches
  • Safari Develop->Page Resources->Network->Ignore Cache
  • Many restarts of Safari
  • Many reboots

Some more things tried since I originally posted:

  • accessing the site from daughter's Chromebook works fine
  • curl on her sitename also retrieves the same error page on her macbook

How Do I Fully Flush Cached Redirects From Safari? seems like it might be relevant? But perhaps not quite the same for Catalina?

Are we missing something obvious? All suggestions much appreciated.

Best Answer

Solved, and obvious in hindsight: there was an entry for her site in /etc/hosts. Sister knows nothing about hostfiles and has no memory of editing it, but provider not so helpfully advises people to edit /etc/hosts to preview Wordpress ahead of domain transfers, and doesn't bother to warn them to clean up after, so we assume that's what happened.