If you're using Sapphire v6, your server must be running RLM v9 or later.  If you are running an earlier version, please update your server to use RLM v9 or newer. You can download the latest version of RLM from here: http://www.genarts.com/support/downloads/rlm.

Check that the date on your computer is correct for both server and client.

Make sure the port numbers used in your server and client license files are the same. The port number is shown after the hostname and Ethernet ID in the HOST line of the license. You can change the port numbers without invalidating the license, but you will need to restart the license server after they are modified. Also make sure this port number doesn't conflict with other applications that might use the same port.

Check the status of your licenses using the RLM server's web interface. From the server machine go to http://localhost:5054 or from another machine use http://servername:5054, replacing server name as appropriate. See if any useful information is shown there. To reread the license file: on the left side of the main page select Reread/Restart Servers, and then on that page click on Reread Licenses.

If all looks OK in the web interface, and the license seems to be up, then make sure you can "ping" the server from the client using the hostname or IP address specified in the license file. (This ensures that the client can get the server's IP address from its hostname, and that there is a working connection between them.) If this doesn't work, try replacing the hostname with the IP address of the license server in the license files.