Timeout during connect (likely firewall problem)

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This is the case for IPv4, however NOT for IPv6:

$ nmap -Pn -p80,443 -6 lokago.de
Starting Nmap 7.95 ( https://nmap.org ) at 2024-10-21 21:58 CEST
Nmap scan report for lokago.de (2a03:b0c0:3:d0::1093:a001)
Host is up.
Other addresses for lokago.de (not scanned): 207.154.228.245

PORT    STATE    SERVICE
80/tcp  filtered http
443/tcp filtered https

Nmap done: 1 IP address (1 host up) scanned in 19.55 seconds
$

Let's Encrypt prefers IPv6. It's strange the challenge even got to the https:// part, as it starts with http://. Although I believe the IPv4 fallback behaves a little bit weird in that in the initial phase there's some fallback being done, but after the redirect not any more.

You need to fix your IPv6. Perhaps a firewall.

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