Remote cluster connect time out

I have two clusters; the remote cluster is single node on AWS. I have set up the same CA on both clusters, but they cannot connect due to time-out issue. Here is the error in log:

[2021-10-13T14:16:49,749][WARN ][o.e.t.SniffConnectionStrategy] [ESnode1] fetching nodes from external cluster [endpoint] failed
org.elasticsearch.transport.ConnectTransportException: [EPnode1][172.32.1.174:9300] connect_timeout[30s]
	at org.elasticsearch.transport.TcpTransport$ChannelsConnectedListener.onTimeout(TcpTransport.java:994) ~[elasticsearch-7.14.1.jar:7.14.1]
	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:673) ~[elasticsearch-7.14.1.jar:7.14.1]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) [?:?]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) [?:?]
	at java.lang.Thread.run(Thread.java:831) [?:?]

And here is my GET _remote/info result:

{
  "endpoint" : {
    "connected" : false,
    "mode" : "sniff",
    "seeds" : [
      "cvrs.**.**.com:9300"
    ],
    "num_nodes_connected" : 0,
    "max_connections_per_cluster" : 3,
    "initial_connect_timeout" : "30s",
    "skip_unavailable" : false
  }
}

I can curl the remote cluster from the local cluster node.

curl -k -u elastic:pass https://cvrs.**.**.com:9200/_cat/nodes?v
ip           heap.percent ram.percent cpu load_1m load_5m load_15m node.role master name
172.32.1.174           11          56   1    0.13    0.04     0.01 dimr      *      EPnode1

Please have a look. Do we have any special config/plugins for AWS server to use Elasticsearch node? Thanks