title: Jenkins 2.89.3 "This Jenkins instance appears to be offline"
body: <p>I have this problem that I can't seem to solve. Using macOS High Sierra.
  I installed Jenkins on my MacBook and I tried to run it on my system but I get this error:
  <a href="https://i.stack.imgur.com/OCpOK.png" rel="nofollow noreferrer">Jenkins message window</a></p>
  
  <p>I have tried the following:</p>
  
  <ul>
  <li>Updated JDK to Update 161 (latest)</li>
  <li>Navigated to: <code>/Users/Shared/Jenkins/Home/hudson.model.UpdateCenter.xml</code> and changed <code>https</code> to <code>http</code></li>
  <li>Uninstalled and reinstalled Jenkins, I have also tried other versions of Jenkins.</li>
  <li>Restart Jenkins service through terminal.</li>
  </ul>
  
  <p>Below is the error message when running <code>java -jar jenkins.war</code> in the terminal which I suspect is the source of the </p>
  
  <blockquote>
    <p>Jenkins appears to be offline</p>
  </blockquote>
  
  <p>and I do not know how to solve this. </p>
  
  <p><a href="https://i.stack.imgur.com/QrCxk.png" rel="nofollow noreferrer">Log file</a></p>
  
  <p>Any help is highly appreciated. Thank you!</p>
  
  <p>David</p>