title: Jenkins : Not able to send slack notifications using Global Slack Notifier plugin 2.18
body: <p>I had Global Slack Notifier version 2.x earlier and it was working fine.
  I migrated to Global Slack Notifier 2.18 plugin and it stopped working. 
  Now, there is NO text-box to enter integration token. 
  Also I have generated the Slack compatible app URL like (edited tokens)</p>
  
  <p><a href="https://hooks.slack.com/services/T6sHRwFeQCH2/BGrKfU7t9K5F/dqPlggttrrffbbgexWClfdVCyG" rel="nofollow noreferrer">https://hooks.slack.com/services/T6sHRwFeQCH2/BGrKfU7t9K5F/dqPlggttrrffbbgexWClfdVCyG</a>
  But it's also not working</p>
  
  <p>Can anyone please correct me if I am missing anything. </p>
  
  <p>Also in /usr/logs/jenkins/jenkins.log file, shows following logs</p>
  
  <pre><code>Mar 01, 2019 5:20:40 PM jenkins.plugins.slack.StandardSlackService publish
  WARNING: Response Code: 404
  Mar 01, 2019 5:20:50 PM jenkins.plugins.slack.StandardSlackService publish
  WARNING: Slack post may have failed. Response: null
  Mar 01, 2019 5:20:50 PM jenkins.plugins.slack.StandardSlackService publish
  WARNING: Response Code: 404
  </code></pre>