Please, try this:
1.- If you have a firewall installed, be sure that port 16720 is open for TCP and UDP protocols.
1.- Open a command prompt window running "cmd.exe" from Start Menu->Run
2.- Test the connectivity using "ping <server>", where <server> is the IP address of your license server.
3.- If it works, run "telnet <server> 16720".
If using the last command you get a prompt and can write some characters, the computer can communicate with the server. If not, there is some network issue.
Was it working before or is this a new installation ? Are there other computers using Forest in your network ?