When I run a test dedicated server from the fs_game root, I get GUID = 0 as well. Always have done, and apparently no way around it, no matter what version and no matter if the Master Server is up or down. I have no idea why or how to fix it. I can only hazard a guess and say that servers which are not listed in the Master Server list, that is, servers which have been up long enough to be registered with the Master Server (some are instantly registered, some take a couple of hours, some take days), will return GUID = 0 because the Master Server is not converting the CD key.