Having the same issue, Press the provision button, unraid working animation for a few seconds, then browser blinks and nothing.
from the logs
Nov 26 17:00:44 Tower emhttpd: shcmd (52225): /usr/bin/php -f /usr/local/emhttp/webGui/include/ProvisionCert.php
Nov 26 17:00:46 Tower root: Error: Server was unable to provision SSL certificate
Nov 26 17:00:46 Tower emhttpd: shcmd (52225): exit status: 1
Nov 26 17:00:46 Tower emhttpd: shcmd (52226): /etc/rc.d/rc.nginx reload
Nov 26 17:00:46 Tower root: Checking configuration for correct syntax and
Nov 26 17:00:46 Tower root: then trying to open files referenced in configuration...
Nov 26 17:00:46 Tower root: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
Nov 26 17:00:46 Tower root: nginx: configuration file /etc/nginx/nginx.conf test is successful
Nov 26 17:00:46 Tower root: Reloading Nginx configuration...