OMERO 5.6 Server is not responding

Dear Omero Team and fellow scientists,

Recently I started to try and setup an Omero.web server for testing in our institute. However, I always run into the same problem. I start the server, get to the login screen, when I try to login, I get the error message: “Server is not responding”. I installed it clear recording to the 5.6 documentation, tried that on Ubuntu 18.04 on 2 different machines and also with the Docker web-standalone container I get the same problem. I did specifically enable the ports with Iptables.
So what am I missing? I would be very grateful if someone could help me on that.

Best wishes,
Nico

What does it show when you run omero admin diagnostics?