OK, here’s your problem: the Let’s Encrypt servers weren’t able to connect to your server. There are many possible reasons for this:
- If your Neth box is behind a firewall, make sure port 80 is open to the Neth box from the whole Internet.
- Make sure your ISP isn’t blocking port 80
- Make sure your DNS records (A/CNAME) are actually pointing to the right IP address (somewhere in that log, it should indicate the IP address it tried to connect to)
- Since Neth still doesn’t do IPv6, make sure you don’t have any AAAA records for this domain name
No, there is no force option for IPv4. If you have IPv6 DNS (i.e., AAAA) records, Let’s Encrypt will attempt to connect using IPv6. If your server doesn’t respond over IPv6 (which Neth doesn’t), the correct solution is to remove those DNS records. If you don’t have AAAA records for that FQDN, Let’s Encrypt won’t attempt to use IPv6.
This would cause exactly the problem that’s happening, if there are still published DNS records pointing to IPv6 addresses.