Hello. I've followed the perfect multiserver guide for Ubuntu 20.04 (https://www.howtoforge.com/tutorial/ispconfig-multiserver-setup-debian-ubuntu) However, I'm able to create certificates for websites but not for the ISPconfig itself on all servers. My setup: panel.domain.com web01.domain.com mx1.domain.com ns1.domain.com In /etc/hosts (for all servers) Code: 127.0.1.1 panel.domain.com panel //different in each one 192.168.0.xxx panel.domain.com panel 192.168.0.xxx web01.domain.com web01 192.168.0.xxx mx1.domain.com mx1 192.168.0.xxx ns1.domain.com ns1 Router configuration: Port 53 is forwarded to the internal IP of ns1.domain.com Port 20,21,80 and 443 are forwarded to the internal IP web01.domain.com Port 8080 is forwarded to the internal IP panel.domain.com All mail ports are forwarded to the internal IP of mx1.domain.com Tried 2 ways: 1. During install 2. I've created a website on panel.domain.com, and then checked SSL and Let's Encrypt SSL In any of the above 2, I get the following error: Code: Checking / creating certificate for panel.domain.com Using certificate path /etc/letsencrypt/live/panel.domain.com Using apache for certificate validation acme.sh is installed, overriding certificate path to use /root/.acme.sh/panel.blacktiehost.com [Wed 23 Feb 2022 05:40:08 PM EET] panel.blacktiehost.com:Verify error:Invalid response from http://panel.domain.com/.well-known/acme-challenge/LZF8ryXK-tK6xb822AFBkZdTLE4fquwwjSFBs2x7z6s [my external IP here]: [Wed 23 Feb 2022 05:40:08 PM EET] Please check log file for more details: /var/log/ispconfig/acme.log Issuing certificate via acme.sh failed. Please check that your hostname can be verified by letsencrypt Log file has record for the same message as above. In my DNS zone, I have: - A record for my primary domain pointing to my external IP - Separate A records for panel, web01, ns1 and mx1 ALL pointing to my external IP I can see that a folder named 'panel.domain.com' is created in /root/.acme.sh in the 'panel' server in any of the above 2 ways, and it's content is: - panel.blacktiehost.com.conf - panel.blacktiehost.com.csr - panel.blacktiehost.com.csr.conf - panel.blacktiehost.com.key Any help appreciated.