title: MongoDB replica creation error: Quorum check failed because not enough voting nodes responded
body: <p>I am trying to deploy MongoDB replica set. I have made my MongoDB instance as primary of the replica in First Digitalocen droplet. Now I am trying to add another MongoDB instance hosted on Second Digitalocen droplet, as secondary of the replica. I have also open 27017 port in the firewall(ufw) with allowing IP address <code>27017 ALLOW Anywhere  27017 ALLOW 206.189.168.245</code></p>
  
  <p>but I am getting the following error:</p>
  
  <pre><code>rs0:PRIMARY&gt; rs.add('206.189.168.245:27017')
  {
      "ok" : 0,
      "errmsg" : "Quorum check failed because not enough voting nodes responded; required 2 but only the following 1 voting nodes responded: 159.89.150.245:27017; the following nodes did not respond affirmatively: 206.189.168.245:27017 failed with Couldn't get a connection within the time limit",
      "code" : 74,
      "codeName" : "NodeNotFound" 
  }
  </code></pre>
  
  <p>Here, Digitalocean droplet version: Ubuntu 16.04.4 x64 and MongoDB version: v3.4.16</p>
  
  <p>What is the reason for this?</p>