title: not able to connect cluster to opscenter
body: <p>hyy folks,
  i have setup cassandra gui using this doc <a href="https://docs.datastax.com/en/install/6.8/install/opscInstallRHEL.html" rel="nofollow noreferrer">https://docs.datastax.com/en/install/6.8/install/opscInstallRHEL.html</a></p>
  <p>but as soon as i hit the url it will open this page</p>
  <p><a href="https://i.stack.imgur.com/utrcV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/utrcV.png" alt="error" /></a>
  here i chosen manage existing clsuter and go to next page
  there it is shown like this
  <a href="https://i.stack.imgur.com/WGXPr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WGXPr.png" alt="iamge" /></a>
  there i paste my private ip
  <a href="https://i.stack.imgur.com/jUNez.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jUNez.png" alt="enter image description here" /></a></p>
  <p>but as soon i hit next it showing this error
  <a href="https://i.stack.imgur.com/Yf0p4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Yf0p4.png" alt="error" /></a></p>
  <p>how can i add my cluster in opscenter</p>
  <p><code>sudo service opscenterd status</code>
  it is showing in Running state</p>
  <p>i entered username and password then it is showing this
  <a href="https://i.stack.imgur.com/kihA1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kihA1.png" alt="enter image description here" /></a></p>