Rancher web UI refused to connect

Here is another post that I refered to:

I check, everything is OK. Just the connection gets refused by the server.
I even run command ufw disable to ensure no firewall blocks it, it still does not allow the connection
I tried Google Chrome, Firefox and Safari, all get the same result, connection refused.
As I mentioned, a month ago I did the exact same steps, it works. Now it does not. And we have not changed anything in our network. We only do sudo apt update and sudo apt upgrade from Ubuntu server to bring the most updates to the server. This probably cause the glitch with the current version of rancher?
Is there a way to pull a rancher log from the Ubuntu server?
Thank you