My domain is: weechat.arnauld.org
I ran this command: na
It produced this output: na
My web server is (include version):
The operating system my web server runs on is (include version):
My hosting provider, if applicable, is:
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): yes and no, I use a web panel and cli.
I installed on my server (which also has a let's encrypt certificate) running Yunohost https://yunohost.org/, the irc client/relay weechat and created a subdomain, weechat.arnauld.org, for it. I installed (but I forgot how 
) a let's encrypt certificate for weechat.arnauld.org so I can connect securely to my weechat relay on my server.
Now I receive an e-mail saying:
Hello,
Your certificate (or certificates) for the names listed below will expire in 19 days (on 17 Jul 20 15:26 +0000). Please make sure to renew your certificate before then, or visitors to your website will encounter errors.
We recommend renewing certificates automatically when they have a third of their
total lifetime left. For Let's Encrypt's current 90-day certificates, that means
renewing 30 days before expiration. See
Integration Guide - Let's Encrypt for details.
But I don't know how I can renew it...
Thank you for any advices and help.
