The V-Ray Licence Server runs as a service on Windows or Mac. By default, it installs with V-Ray (unless you choose not to install it) and when running, it can be viewed in your browser at: http://localhost:30304
See 'Understanding the V-Ray Licence Server' for more information on the interface you should expect to see.
Common Problems
Because it runs as a service, it can stop. Sometimes it doesn't start correctly immediately after installation. The first and simplest thing to do is restart your machine. Very often, this is enough to get the service to start up.
If restarting doesn't fix it, it could mean it's not installed correctly. The best thing to do at this point is re-run your V-Ray installer and select only the licence server (on Windows, always install as administrator). This will install the licence server but not affect your V-Ray installation. It may work straight away, or need a restart. Check in a browser at: http://localhost:30304
If It Still Doesn't Work..
If you want to check Licence Server Processes:
On Windows, open the Task Manager (Ctrl+Alt+Delete), on Mac, open Activity Monitor.
View processes (select all users), you should see two processes running: