aving debug log to /var/log/letsencrypt/letsencrypt.log
Please enter the domain name(s) you would like on your certificate (comma and/or
space separated) (Enter 'c' to cancel): ferienhofkleingarn.ddns.net
Requesting a certificate for ferienhofkleingarn.ddns.net
Hint: The Certificate Authority failed to verify the temporary nginx configuration changes made by Certbot. Ensure the listed domains point to this nginx 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.
The operating system my web server runs on is (include version): Debian 8 (Jessie)
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): certbot 1.19.0
My Problem was that my Webserver was using the Port 8443,
but the Check is only getting passed when the Website stays at Port 80.
So i temporarily setup a new Webserver which keeps at Port 80 (Default NginX Page).
Then i was able to generate my Certificate.
After that i successfully importet my Certificate into My Webserver
Hmm. I am seeing a self-signed cert in openssl and an expected browser warning about such.
openssl s_client -connect ferienhofkleingarn.ddns.net:8443 -servername ferienhofkleingarn.ddns.net -trusted_first
CONNECTED(00000003)
depth=0 C = US, ST = CA, L = San Jose, O = Ubiquiti Networks Inc., OU = UniFi Protect, CN = CloudKey
verify error:num=18:self signed certificate
verify return:1
depth=0 C = US, ST = CA, L = San Jose, O = Ubiquiti Networks Inc., OU = UniFi Protect, CN = CloudKey
verify return:1
---
Certificate chain
0 s:/C=US/ST=CA/L=San Jose/O=Ubiquiti Networks Inc./OU=UniFi Protect/CN=CloudKey
i:/C=US/ST=CA/L=San Jose/O=Ubiquiti Networks Inc./OU=UniFi Protect/CN=CloudKey
You may have gotten a proper cert but your server is not yet sending the new fullchain.
A couple things. You gave an example certonly command. Did you need any other updates to your nginx conf manually to use the new certs? You said you imported it so you should double check that. I am not sure what you mean by imported.
If that is all good, did you reload nginx to pickup the new config?