If you get this type of error while installing a secondary server

1. Verify if there is not Firewall or Proxy blocking outboud connection to Primary, or that it is setup with proper ports open
2. Check connectivity on TCP port 2560 and HTTPS port 7300:

   telnet <primary-server> 7300

   $ telnet primary.eu.eophcp.com 7300
   Trying 192.168.1.18...
   Connected to primary.eu.eophcp.com.
   Escape character is '^]'.

3. Verify Primary server replies back using the Public API with CURL on port 7300:

   curl -k -v -H X-Api-Key:46405b18-8e1b-4db9-b930-bedd9ae839af https://primaryaddress:7300/api/v1/version

   $ curl -k -v -H X-Api-Key:46405b18-8e1b-4db9-b930-bedd9ae839af https://primary.eu.eophcp.com:7300/api/v1/version
   
   * About to connect() to primary.eu.eophcp.com port 7300 (#0)
   * Trying 34.252.199.173...
   * Connected to primary.eu.eophcp.com (34.252.199.173) port 7300 (#0)
   * Initializing NSS with certpath: sql:/etc/pki/nssdb
   * skipping SSL peer certificate verification
   * SSL connection using TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
   * Server certificate:
   * subject: CN=*.eu.eophcp.com
   * start date: Oct 11 00:00:00 2019 GMT
   * expire date: Nov 09 12:00:00 2021 GMT
   * common name: *.eu.eophcp.com
   * issuer: CN=RapidSSL TLS RSA CA G1,OU=www.digicert.com,O=DigiCert Inc,C=US
   > GET /api/v1/version HTTP/1.1
   > User-Agent: curl/7.29.0
   > Host: primary.eu.eophcp.com:7300
   > Accept: */*
   > X-Api-Key:46405b18-8e1b-4db9-b930-bedd9ae839af
   >
   < HTTP/1.1 200 OK
   < Date: Mon, 12 Oct 2020 16:38:37 GMT
   < Content-Type: application/json
   < Content-Length: 109
   <
   * Connection #0 to host primary.eu.eophcp.com left intact
   {"version":"3.8.1-release-1-g6d72427cb","buildDate":"2020-09-10 21:38:53.535","buildTimeStamp":1599766733536}