title: Why does Jenkins say "This Jenkins instance appears to be offline"
body: <p>I have a fresh install of Jenkins 2.32.2 on Ubuntu.
  Opened a browser on the instance and get to a page titled <strong>Offline</strong>, with the message <strong>"This Jenkins instance appears to be offline"</strong> and offers options to "Configure Proxy" or "Skip Plugin Installation"</p>
  
  <p>The machine clearly isn't offline as I just used the internet connection to do the installation.
  I also had a previous installation, done exactly the same way, that was working.
  I removed the previous installation as Pipelines wouldn't work and Google told me it was because of JDK 9. So I removed all the JDK/JRE installations as well as jenkins, fresh installed JDK 8 only, installed Jenkins, and got to here.</p>
  
  <p>Jenkins has worked on this box in the past so what makes it think it is offline?</p>
  
  <p><strong>Update:</strong> Found a log file /var/lib/jenkins/logs/tasks/Download metadata.log
  and it starts with a message <strong>FATAL: Connection refused (Connection refused)</strong>
  I would think that indicates that the internet connection is OK, but something else is stopping it getting data?</p>
  
  <p><strong>Update:</strong> Based on other research I checked the Update Site in the Plugin Manager. This is listed as <a href="http://updates.jenkins-ci.org/update-center.json" rel="noreferrer">http://updates.jenkins-ci.org/update-center.json</a> and, from the command line a wget of this file succeeds. So most definitely not a connection issue. Worked with both http and https, jenkins works with neither.</p>