In the installation guide, before the step where it says to run the following,
certbot certonly --standalone --preferred-challenges http -d yourinstance.tld
Add step to stop nginx first.
sudo systemctl stop nginx
The following error is displayed if you do not stop nginx first.
EDIT: There’s also another error message that’s displayed even if it’s not for a cert renewal. So it’s critical that this step is added.
Attempting to renew cert from /etc/letsencrypt/renewal/somedomain.com.conf produced an unexpected error: Problem binding to port 443: Could not bind to IPv4 or IPv6.. Skipping.