If you ask 6 people that question you will probably get 6 different answers. Network configurations vary so much. Here is my attempt:
When the radio was connected to the computer, most likely DHCP was used. Now, with the change, it has to be on the subnet of your network. So did you set all network components to fixed ip addresses (computer and switch if can be) and did you do the following for the radio?
1- Connect the computer directly (not through the router) to the radio through an ethernet cable.
2- Configure the computer's network card to use an IP address of the same class as the radio, for example 192.168.16.15.
3- Restart the computer and, if the radio was on, you should turn it off and on again.
4- Start ESDR2 and, from the Options-Devices-> menu, search for the radio.
5- Once the radio has been found, click on the Use button and then move to the Expert panel.
6- In the New IP Address area set the new IP address (possibly also the port) and click on the Set IP Address button. For example you can give the address 192.168.0.12. (whatever your router subnet is so it might be 192.168.1.xx)
7- Close EESDR and turn off the radio.
8- Return to the computer's network settings and restore the default settings (those that allow the PC to connect to your internet).
9- Restart the computer.
10- In the meantime connect the radio to the router and turn it back on.
11- Check that the computer is on the network and that the LED of the Sun is green. At this point, by opening ESDR2 it will be possible to start using the radio and should be connectable from any PC on the network.
If there is still a failure check that you can ping all components.
But any networking guru may have corrections to the above - this is how I did it but, as I said, networks vary.