Free SSL certs for your znc instance? Follow the steps:

30 */12 * * * /usr/bin/letsencrypt renew >> /var/log/le-renew.log; cat /etc/letsencrypt/live/srv08.karloluiten.nl/privkey.pem /etc/letsencrypt/live/srv08.karloluiten.nl/cert.pem /etc/letsencrypt/live/srv08.karloluiten.nl/chain.pem /etc/letsencrypt/dhparam.pem > /home/user/.znc/znc.pem