System registration fails with error Connect to sso.redhat.com:443 failed: Connection refused

Issue

• Unable to register the system using subscription manager
• System registration fails with error HTTP error (401 - Unauthorized): HTTP Request failed
• Registration of the system fails with below error

   # subscription-manager register 
    Username: ****** 
    Password: 
    HTTP error (401 - Unauthorized): HTTP Request failed: org.apache.http.conn.HttpHostConnectException: Connect to 
    sso.redhat.com:443 [sso.redhat.com/xx.xx.xx.xx] failed: Connection refused (Connection refused)