let`s encryptからメールが届いて、証明書の有効期限が近付いているとのこと

cronで自動更新の設定をしているのでなぜだろうとログを確認
更新が成功する証明書もあるものの、何故か一つだけ更新が失敗している様子

The following certs were successfully renewed:
  /etc/letsencrypt/live/*******/fullchain.pem (success)
  /etc/letsencrypt/live/*******/fullchain.pem (success)
  /etc/letsencrypt/live/*******/fullchain.pem (success)
  /etc/letsencrypt/live/*******/fullchain.pem (success)

The following certs could not be renewed:
  /etc/letsencrypt/live/*******/fullchain.pem (failure)

手動で更新を試みるも失敗する

[root@f1-micro-us-central ~]# /usr/local/certbot/certbot-auto certonly --manual -d [ドメイン]
our system is not supported by certbot-auto anymore.
certbot-auto and its Certbot installation will no longer receive updates.
You will not receive any bug fixes including those fixing server compatibility
or security problems.
Please visit https://certbot.eff.org/ to check for other alternatives.
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator manual, Installer None
Cert is due for renewal, auto-renewing...
Renewing an existing certificate for [ドメイン名]
Performing the following challenges:
http-01 challenge for [ドメイン名]

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Create a file containing just this data:

alayKONps9DubcYrnivTAp84bG8NUz4XXhLmpNhg4fE.O5P34-wyybkmxc1-Bj2ii0G8ff_4T5pULJkxmIUMmy8

And make it available on your web server at this URL:

http://[ドメイン名]/.well-known/acme-challenge/alayKONps9DubcYrnivTAp84bG8NUz4XXhLmpNhg4fE

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Press Enter to Continue
Waiting for verification...
Challenge failed for domain [ドメイン名]
http-01 challenge for [ドメイン名]
Cleaning up challenges
Some challenges have failed.

IMPORTANT NOTES:
 - The following errors were reported by the server:

   Domain: [ドメイン名]
   Type:   unauthorized
   Detail: Invalid response from
   https://[ドメイン名]/.well-known/acme-challenge/alayKONps9DubcYrnivTAp84bG8NUz4XXhLmpNhg4fE
   [IPアドレス]: "<!DOCTYPE html><html><head><meta name=\"viewport\"
   content=\"width=device-width\"/><meta
   charSet=\"utf-8\"/><title>404: This page coul"

   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.

以下のメッセージに添って静的コンテンツを配置してみた

Create a file containing just this data:

alayKONps9DubcYrnivTAp84bG8NUz4XXhLmpNhg4fE.O5P34-wyybkmxc1-Bj2ii0G8ff_4T5pULJkxmIUMmy8

And make it available on your web server at this URL:

http://[ドメイン名]/.well-known/acme-challenge/alayKONps9DubcYrnivTAp84bG8NUz4XXhLmpNhg4fE

再度手動更新したところ無事更新された

Press Enter to Continue
Waiting for verification...
Cleaning up challenges

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/[ドメイン名]/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/[ドメイン名]/privkey.pem
   Your cert will expire on 2022-04-07. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot-auto
   again. To non-interactively renew *all* of your certificates, run
   "certbot-auto renew"
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

今回だけだったのか原因は不明、
3か月後にまた同じように自動更新されなければ再度調査が必要