Datastax Agent (Cassandra) Opscenter setup issue

I've setup opscenter on one of cassandra cluster nodes. After installation, when setting up my cluster, I tried installation of datastax agent on all the cluster nodes via UI, but it failed. So, I had to install the agents manually.

After manually installing the agents, the node in which opscenter is installed is able to connect, but not the other nodes. It still says, "2 agents failed to connect". What could be the issue?

PS : My cassandra cluster is setup on AWS.