There is a tool called tentacle ping/pong test that verifies that the tentacle is available on the target endpoint.
I've not been able to add a endpoint to octopus, that is my issue.
When i monitor the firewall logs i can see that the octopus server isn't even attempting to communicate over the internet. If i post the endpoint url in a browser on the octopus server i can see the logs appear in the firewall. So i know that the octopus server can hit that endpoint, i know that the tentacle is available following the ping/pong test so it looks like octpus console doesn't call out over the internet.