If your Let's Encrypt SSL certificate is needing to be renewed, here is how to simply do it (assuming you are on a Linux or Ubuntu server).
***Make sure you have installed certbot, see this article for more info: Install and Secure UniFi Cloud Controller on Amazon Web Services - SimpliWiFi | Event Technology Services
Assuming all that, simply run these commands:
1 - sudo su
2 - sudo certbot --apache -d [your unifi domain here]
3 - sudo /usr/local/bin/unifi_ssl_import.sh
4 - Done!
