I have exactly the same issue as this post 3 years ago. Certbot timer is working, but the cert will not renew every 90 days. I resorted to booting the server and the cert will be updated. I have also shown my certbot system status and certbot.service. Previously, it was mentioned that this could be due to permission, but it is unlikely since the cert is updated upon reboot. What could be the problem here? Thank you.
[] [1]: Certbot renew running but not renewing
super@mail:~$ sudo systemctl status certbot
● certbot.service - Certbot
Loaded: loaded (/lib/systemd/system/certbot.service; static; vendor preset: enabled)
Active: inactive (dead) since Mon 2021-09-06 15:21:02 +08; 2h 42min ago
Docs: file:///usr/share/doc/python-certbot-doc/html/index.html
https://letsencrypt.readthedocs.io/en/latest/
Main PID: 19282 (code=exited, status=0/SUCCESS)
Sep 06 15:21:01 mail systemd[1]: Starting Certbot...
Sep 06 15:21:02 mail systemd[1]: certbot.service: Succeeded.
Sep 06 15:21:02 mail systemd[1]: Started Certbot.
super@mail:~$ cat /lib/systemd/system/certbot.service
[Unit]
Description=Certbot
Documentation=file:///usr/share/doc/python-certbot-doc/html/index.html
Documentation=https://letsencrypt.readthedocs.io/en/latest/
[Service]
Type=oneshot
ExecStart=/usr/bin/certbot -q renew
PrivateTmp=true