I´ve followed the excellent tutorial: "The Perfect Server - Debian 10 (Nginx, BIND, Dovecot, ISPConfig 3.1)" and almost everything runned fine, except in the part where ISPConfig runs acme.sh to issue the certificate. It gives an error: "Verify error:Fetching http://debian10.mydomain.com/.well-known/acme-challenge/xbtyIhFqLmguqTKHLEx-4AJ4iJDn3vnVs86pyDLydQ8: Connection refused". It says also that I need to check if my hostname can be verified by letsencrypt and because of that error it fall-back to a self-signed certificate. In fact, that domain really is not accessible when browsing in Chrome, it shows the same error: "Connection refused". But the domain, and its subdomain was already active and configured in the DNS table, so it is completely accessible. What can I do to unblock that url in order to letsencrypt verify the domain and issue the certificate correctly? Note: I am using ISPConfig 3.2.