These kind of errors normally you would need to closely work with your network team/TP side folks to resolve it quickly…But based on the error above it indicates remote server/host is not accepting any of your requests (inbound to TP)…Definetely some thing related to firewall/https certs issue troubleshooting needed:
It’s tough call to say exactly whats going on with in your network layers etc…or some protocol fixes needed:
Even if the target server is up and running it may not be reachable from your network. From the unix box (of the TN/IS) do a
telnet host port
or ask your system admin do make sure the connectivity is fine. As RMG suggested, you should pull the firewall/network team in. All the best