When you did the install did you select auto or manual start up for the server sofware when the computer starts up?
If you set it to manual then you will have to go into the FMP Server Console and go to "Services(local), expand the tree and from the window on the right find FM Server, click on it to highlight it and then go to the Action menu on the main menu and select "Start". This will start the server and open all files that are placed in its directory. This is also a quick way to see it the server software is running (if you do not know your way around windows), because if it is running then the option available will be "Stop."
Is TCP/IP set up as the protocol on all machines?
Have you set up the software for number of users, hosted files, etc, etc.?