The thing with our Softaculous setup is that it’s not exposed on the standard HTTP/HTTPS port, but on a special port 2082. Some restrictive firewalls block all unknown ports and will also block access to Softaculous.
This is not just a problem for Softaculous though. Premium cPanel makes use of various custom ports for cPanel, WHM and Webmail as well. So having such a restrictive firewall causes problems on many web hosting services.