1) that PC with Radmin server has an access to Radmin activation server PC
2) that you've entered correctly your license key and address/port of you activation server to .msi if you are unsure please create a tech support ticket and attach a screenshot of these pages in .msi
Enter your license code into registration box (don't press OK)
Choose checkbox "Manual activation"
Save *.request file
Go to activation server (http://activate.famatech.com/)
Upload your *.request file
The activation server will return you *.license file
Save it somewhere on your computer
Go to activation box again, choose "use license file" and specify a path to your *.license file recieved from activation server.
You copy will be registered.
You are also able to activate license code remotely form the PC where activation was successful.
To do this open the Viewer on the PC where activation was successful, right click on connection icon of the target PC and choose "Transfer license code".