Please restart the sshd service in each node and try to ssh login from namenode to each node.

1) To restart sshd service :

sudo service sshd restart

2) For ssh login to other node from namenode:

ssh hostname_of_destination_node


ssh ip_of_destination_node

I think this will resolve the query.

Please let me know if the issue still persists.

Feel free to contact us in case you have any other query.