IPv4 and IPv6 is enabled, DNS-Settings are correct. According to the web host (Dogado) there are no restrictions on their side. Even with the firewall disabled and Fail2Ban disabled, I don't get a certificate. I'm trying to generate the certificate with only root and WWW domain, no wildcard, no email.
My web server is: nginx/1.22.1
The operating system my web server runs on is: Ubuntu 22.04.2 LTS
Yes, I can login to a root shell on my machine.
I'm using Plesk 18.0.52 Update #3 to manage my site.
One is your IPv6 AAAA address cannot be used to reach your domain. See below and Let's Debug test site (link here)
curl -I4 http://24plus.de
HTTP/1.1 301 Moved Permanently
Location: https://24plus.de/
curl -I6 http://24plus.de
curl: (7) Failed to connect to 24plus.de port 80 after 10289 ms: No route to host
Two, your nginx is not handling the HTTP Challenge request from the Let's Encrypt server correctly. It is redirecting it back to your home page. It must return the challenge request token placed on your server by Plesk's ACME client. Review your Wordpress and/or nginx redirects
(this redirect is ok although best if handled in port 80 server block)
curl -I4 http://24plus.de/.well-known/acme-challenge/Test123
HTTP/1.1 301 Moved Permanently
Server: nginx
Location: https://24plus.de/.well-known/acme-challenge/Test123
(this redirect fails as redirects to home page)
curl -I4 https://24plus.de/.well-known/acme-challenge/Test123
HTTP/2 301
server: nginx
location: https://24plus.de/
x-redirect-by: WordPress
x-powered-by: PleskLin