[404] Unable to Get Certificate for Matrix

[NoteStars]

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. crt.sh | 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: matrix.notestars.me

I ran this command: sudo certbot certonly --standalone -d matrix.notestars.me

It produced this output: Certbot failed to authenticate some domains (authenticator: standalone). The Certificate Authority reported these problems:
Domain: matrix.notestars.me
Type: unauthorized
Detail: 5.78.78.247: Invalid response from http://matrix.notestars.me/.well-known/acme-challenge/ZmakQBfK97Hcs2T-jHv2RKlMLNdbVeNx-aF1Fz_CULM: 404

My web server is (include version): 1.24.0-2ubuntu7.5

The operating system my web server runs on is (include version): Ubuntu 24.04 LTS

My hosting provider, if applicable, is: Hetzner

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):

The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): certbot 2.9.0

[MikeMcQ]

You have something listening for HTTP on port 80 and always giving a reply of 404 Not Found.

When using Certbot --standalone it requires exclusive use of port 80. It usually shows a message when it fails to open port 80.

What do you have that is replying to HTTP requests? Once we know that we can give better advice on how to proceed.

curl -i http://matrix.notestars.me/ 

HTTP/1.1 404 Not Found
Content-Type: text/plain; charset=utf-8
X-Content-Type-Options: nosniff
Date: Fri, 13 Feb 2026 21:07:56 GMT
Content-Length: 19