Update certificate error

[achan]

I tried to update the certificate, but I got an error.
The executed command is “letsencrypt-auto certonly --standalone --preferred-challenges http-01 -d example.com --agree-tos -n”.
The execute this command PC and web server (domain) are differtent PCs.
When executed this command 2 month ago, it was successfully updated certificate.
I don’t know why this time is failed,
and I don’t know why to access the web server even though I specified “standalone”,
please help me.

The executed command logs are following,

Requesting to rerun letsencrypt-auto with root privileges…
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator standalone, Installer None
Cert is due for renewal, auto-renewing…
Renewing an existing certificate
Performing the following challenges:
http-01 challenge for example.com
Waiting for verification…
Cleaning up challenges
Failed authorization procedure. example.com (http-01): urn:acme:error:unauthorized :: The client lacks sufficient authorization :: Invalid response from http://example.com/.well-known/acme-challenge/xxxxxxxx [IP Address]: 404

IMPORTANT NOTES:

• The following errors were reported by the server:

  Domain: example.com
  Type: unauthorized
  Detail: Invalid response from
  http://example.com/.well-known/acme-challenge/xxxxxxxx [IP Address]: 404

  To fix these errors, please make sure that your domain name was
  entered correctly and the DNS A/AAAA record(s) for that domain
  contain(s) the right IP address.

[_az]

Standalone just means that Certbot will start its own web server instead of using your existing one to host the challenge file.

If your domain isn’t pointing at the standalone server, then it will fail, as Let’s Encrypt isn’t able to reach the challenge file over HTTP, and you get this kind of error.