I am not getting it. As I mentioned before there is no geo-blocking configured and not sure why introducing ipv6 would help as it world introduce more untested unknowns. I can also say that with the exception of the domain name there is nothing different between the working and non working domains. They all have the same IP, Identical DNS records, host, domain registrar, same location and in some y cases the same content.
You were not asked to introduce ipv6. Does name service return IPv6 addres for that problem domain? If it does, Let's Encrypt tries to access the site using IPv6, and fails if you server has not set up IPv6. The debug log has: Code: 16.05.2023-18:02 - DEBUG [letsencrypt.inc:468] - LE CERT OUTPUT: Expiry Date: 2022-10-19 07:04:38+00:00 (INVALID: EXPIRED) That certificate seems to have expired last year at October. Does this provide clues on what might have happened? Code: Saving debug log to /var/log/letsencrypt/letsencrypt.log Have you looked at that file, maybe there is more information there? If problem still persists, I would say you either have to pay for support using https://www.ispconfig.org/support/ using ISPConfig Business Support, or reveal what the FQDN domain name is so users here on this forum can check what is going on.
