Firewall, Anti-Virus, NAT, TCP Ports are shut down, LFS is blocked usually by these.
Or there is that you must have put your password "online" or "activated". Just go to your account on
www.lfs.net, and log in. Then, go to account details, and put your GAME-passwords, at least 8 characters, and then go to LFS game, LFS.EXE, press your account name on entry screen, then, Open your Demo-license by your GAME passwords what you have putted on your account details in lfs websites.
That should work