help with generating ssl for freedns in nginx

Hi,

I've been following this guide to set up some basic selfhosted services (video) https://www.youtube.com/watch?v=qlcVx-k-02E (text) https://notthebe.ee/blog/easy-ssl-in-homelab-dns01/

I've managed to get things working, but DuckDNS (duckdns.org) seems to be unresponsive most of the time. I then tried to register my DNS at FreeDNS (freedns.afraid.org), but the generation of a ssl certificate in Nginx fails. I get the following error message in Nginx:

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

    at /app/lib/utils.js:16:13
    at ChildProcess.exithandler (node:child_process:430:5)
    at ChildProcess.emit (node:events:518:28)
    at maybeClose (node:internal/child_process:1104:16)
    at ChildProcess._handle.onexit (node:internal/child_process:304:5)


  

The domain I chose is

<my_subdomain>

Does anyone know how I can get Nginx to succeed in generating the ssl certificate so I don't have to start deploying ssl generation myself?

If I have to do it myself any useful resources will be appreciated.

Thanks :)