HTTPS/SSL not working with Cups
Solution 1:
Copy your SSL (example LetsEncrypt ) to cups directory, as shown below:
cat /etc/letsencrypt/live/yourdomain.com/fullchain.pem >> /etc/cups/ssl/server.crt
cat /etc/letsencrypt/live/yourdomain.com/privkey.pem >> /etc/cups/ssl/server.key
restart cups-server:
systemctl restart cups # on CentOS