SSL failed on Apache 2 Ubuntu 20.04

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My domain is: http://kstrjannik.de/

I ran this command: sudo certbot --apache

It produced this output:
space separated) (Enter 'c' to cancel): kstrjannik.de
Requesting a certificate for kstrjannik.de

Certbot failed to authenticate some domains (authenticator: apache). The Certificate Authority reported these problems:
Domain: kstrjannik.de
Type: unauthorized
Detail: Invalid response from http://kstrjannik.de/.well-known/acme-challenge/w7q-8V6NpUF2oQLeuL4PIW62qwylTSe7_cX4_D-qvR4 [2001:8d8:100f:f000::257]: 204

Hint: The Certificate Authority failed to verify the temporary Apache configuration changes made by Certbot. Ensure that the listed domains point to this Apache server and that it is accessible from the internet.

Some challenges have failed.
Ask for help or search for solutions at https://community.letsencrypt.org. See the logfile /var/log/letsencrypt/letsencrypt.log or re-run Certbot with -v for more details.

My web server is (include version):

Server version: Apache/2.4.41 (Ubuntu)
Server built: 2020-08-12T19:46:17

The operating system my web server runs on is (include version): Ubuntu 20.04

My hosting provider, if applicable, is: Hetzner.com

I can login to a root shell on my machine (yes or no, or I don't know): yes

I'm using a control panel to manage my site (no, or provide the name and version of the control panel): no

The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): 1.16.0

The Let's Encrypt validation server reports it used an IPv6 address to connect to your site. However, currently I'm not seeing any AAAA resource records for kstrjannik.de. Did you by any chance remove this very recently?