Hi,
Assuming you are not working with http/SSL.
To access NCS from the public side it is no need for a certificate. Since everything is working on the LAN side it seems to be a setup in the router.
Here is the guide on how to … Accessing Netcam Studio remotely using Web Client or Smartphone App
Only port 8100 need to be forwarded in the router.
When you test with the Android app and the public IP make sure that the smart phone do not work on LAN wifi.
When you start a browser on the Windows computer (on the public side) enter http://publicIP:8100 Is that working?
If you start the Windows client, red icon, on the computer on the public side you must forward ports 8100, 8120 and 8124.
Do you use the correct public IP to the router. Sometimes the ISP gives you a “public IP” that actually is a LAN IP to save addresses.
-Henrik