We are having the exact same problem described here:
The poster doesn’t receive a (public) reply after his last post, is there really nothing that can be done about this? It seems that the “use IE proxy” setting is just not working - I can access our feed fine in IE, but the test tool in Octopus gives “Unable to connect to remote server”.
Thanks for reaching out. Could you try running the Octopus Server service with your own user account and password? By default it runs under Local System, and setting it up with your account or a service account might be what it needs to go through the proxy.
Let me know how it goes
This was indeed the problem