This is a diagram of how connections work to your PNPSCADA Server

Your server is the one in the middle
Updates and Backups are done from the update server (in Germany) over TCP port 22 incoming to your server.
For updates and backups to happen, the update server needs to be able to connect to your server on a public IP.
Licensing is done from the Licensing Server over TCP port 12345 outgoing to the Licensing Server.
For licensing to happen your server needs internet, but does not need a public IP.
Browsing your server is done from your PC/Phone over TCP port 80 or 443 incoming to your server.
If you don't have a public static internet IP, you will not be able to browse your server from outside of your server farm.
Modems could connect to Your Server, and Your Server could connect to modems depending on which modems you use.
Depending on which modems you use, the ports needed varies.
For generic modems, we allocate ports between the range of 13000-14000 (TCP incoming).
But other ports are also used such as 7627,56267,7259,2223,2224,2225,2226,2227,2228,2229,2230,8265 and 23000-24000
The modems are programmed with the server's IP and the port that was allocated for them.
Generally speaking, if you do not have a public static IP, the modems will not have a place to connect to and you wont be able to read any meters.