Hi Kevin,
Sorry for the late response,
According to the error message, could be some issue with the access to ports 80 or 443, you will need to verify if they are open.
You can execute this.
netstat -tunap| grep ":80\|:443"
Also, please verify the log error on /var/log/letsencrypt/
letsencrypt.log
Looking forward to your update.
Regards
Marcos.