title: Coordinator node failed to join the elasticsearch cluster
body: <p>I am trying to add a coordinator node to my cluster, but I am facing this error when I run it :</p>
  <pre><code>[2020-09-22T14:03:00,808][INFO ][o.e.c.c.JoinHelper       ] [coordinator-node] failed to join {MASTER-02}{7ZSdp7FQQaa_34eM2LQzjA}{-HOAFDSlSF-iDOnE4ZSdFg}{10.13.81.12}{10.13.81.12:9300}{dilmrt}{ml.machine_memory=8365060096, ml.max_open_jobs=20, xpack.installed=true, data=hot, transform.node=true} with JoinRequest{sourceNode={coordinator-node}{Wb5iaDUWS5qKmiO7P9ABEg}{KvuU9jjPROCcCFdHyvon1g}{10.13.81.40}{10.13.81.40:9300}{xpack.installed=true, transform.node=false}, minimumTerm=74, optionalJoin=Optional[Join{term=74, lastAcceptedTerm=0, lastAcceptedVersion=0, sourceNode={coordinator-node}{Wb5iaDUWS5qKmiO7P9ABEg}{KvuU9jjPROCcCFdHyvon1g}{10.13.81.40}{10.13.81.40:9300}{xpack.installed=true, transform.node=false}, targetNode={MASTER-02}{7ZSdp7FQQaa_34eM2LQzjA}{-HOAFDSlSF-iDOnE4ZSdFg}{10.13.81.12}{10.13.81.12:9300}{dilmrt}{ml.machine_memory=8365060096, ml.max_open_jobs=20, xpack.installed=true, data=hot, transform.node=true}}]}
  </code></pre>
  <p>And the error in the master node is :</p>
  <pre><code>[2020-09-22T14:00:14,731][WARN ][o.e.c.c.Coordinator      ] [MASTER-02] failed to validate incoming join request from node [{coordinator-node}{Wb5iaDUWS5qKmiO7P9ABEg}{KvuU9jjPROCcCFdHyvon1g}{10.13.81.40}{10.13.81.40:9300}{xpack.installed=true, transform.node=false}]
  org.elasticsearch.transport.RemoteTransportException: [coordinator-node][10.13.81.40:9300][internal:cluster/coordination/join/validate]
  </code></pre>
  <p>The configuration of the coordinator node is:</p>
  <pre><code>cluster.name: ClusterName
  node.master: false
  node.data: false
  node.ingest: false
  network.host: 10.13.81.40
  http.port: 9200
  discovery.seed_hosts: [&quot;@IP Master-1&quot;, &quot;@IP Master-2&quot;, &quot;@IP Master-3&quot;]
  cluster.initial_master_nodes: [&quot;name master-1&quot;, &quot;name master-2&quot;, &quot;name master-3&quot;]
  
  </code></pre>
  <p>Could someone tell me where is the mistake please !
  Thanks for your help :)</p>