I couldn't start the service without setting the /etc/hosts file, but found the fault. It was not IPv6 related as disabling this did not resolve the issue. It was iptables blocking the port 80 connection.
Modifying /etc/sysconfig/iptables to allow 80 and 443 now works remotely.
I cannot test the connection or register tgw, I get the following error in the logs
Yes, the first release of 3.5 had a problem with the production certificate included in the download.
Engineering released a new version late yesterday with a fix. Please download the new version and re-install.
Alternatively, you can clear that error by deleting lb_truststore.jks from tg/resources/security and restarting the process. I'll provide the full path in a moment. But I would recommend installing the latest version.