In the office where i work we have 7 machines. They all use the same software and the licence is present only on one of them while the other machines are aiming to it via IP address. The problem is that often after restarting the machine the IP changes so i have to go through the other 6 machines and change the IP address in the license tool.
How can fix the IP of the machine that has the license so that it remains the same afer each restart? I tried to follow a guide like this: https://www.makeuseof.com/tag/static-ip-address-advantages-disadvantages/ but i can't find anything similar in the router setting (i have a TC7200)
You shouldn't lose internet connection assuming you entered the correct values for the Gateway and DNS Servers (and the static IP address itself of course).
Put it back to dynamic IP address, reboot, and then copy down all the values. Enter those when changing it to a static IP address. Unfortunately this is one of those things that someone with knowledge could do, sitting in front of your PC, in about 10-15 minutes but it'd take ages to try and explain it remotely like this.
Is this your modem?
If so, I can't see any way to create static IP addresses in the router. The Connect Box has this feature if you decide to upgrade to one of those. However, another way would be to configure your licence server itself to not use DHCP but instead use a fixed IP address.