The Certificate Authority failed to verify the temporary nginx configuration changes made by Certbot

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1

Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.

My domain is: jellyfin.rimusa.me

I ran this command: sudo certbot --nginx -d jellyfin.rimusa.me

It produced this output:
Certbot failed to authenticate some domains (authenticator: nginx). The Certificate Authority reported these problems:
Domain: jellyfin.rimusa.me
Type: connection
Detail: 46.239.112.183: Fetching http://jellyfin.rimusa.me/.well-known/acme-challenge/omSFNCQNcAe4tkpdAbPsjfMIJpaGNZwnZjkQYuOTK_w: Timeout during connect (likely firewall problem)

My web server is (include version): jellyfin 10.11.6

The operating system my web server runs on is (include version): Ubuntu Server 25.10

My hosting provider, if applicable, is: selfhosted

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 4.0.0

2

The --nginx option uses the HTTP Challenge method to prove you control that domain name. That requires an HTTP request from the Let's Encrypt server to be able to reach you from the public internet.

It looks like you are not allowing any connections from anywhere on the public net. Not even for your "home" page. See: Check website performance and response : Check host - online website monitoring

It may not be a firewall like suggested in the message. It might just be incorrect communications config in your system.

You will need to get HTTP requests on port 80 working before a cert request using --nginx will work

3

You may have changed things since posting this, but I can’t access this URL, or connect to your domain at all over HTTP. That probably means that your CA can’t either.

Maybe try from your phone or some other external device to see if you can hit that URL and troubleshoot from there.

4

Thanks for the responses! I finally managed to solve it, here were the issues/tells for reference:

  • I had enabled ports 80 and 443 both on the server and the router, as well as a higher port
  • This higher port accepted connections as expected
  • I could connect to port 80 via http to the server on my home network
  • Connections from outside were not accepted (e.g. when using a VPN or when connecting via check-host.net)

Turns out that my ISP has a portal where I had to allow for http and https connections to my home network (but higher ports were allowed by default for some reason). I have changed this and was able to get certbot to work as expected, so now my domain allows for both http and https connections.

5

Just so we can help other people with the same ISP, would you mind telling us who your ISP is?

6

It's via SGS in Sweden, the website to change these settings is hemma.sgs.se - of note is that you need to be connected to your home network to be able to access this site