Generally, when you get a -15 error it is because the client machines cannot see the license server. That is often caused by the Windows Firewall or the fact that the NLM is not configured to run as a Service.
Error 1.5.-15: Cannot connect to license server system.
The server (lmgrd) has not been started yet, or the wrong port@host or license file is being used, or the TCP/IP port or host name in the license file has been changed.
Make sure you choose 'Configuration using Services' on the Server/License File tab and check the box to ignore the environment variable. Then make sure both checkboxes are checked at the bottom of the Config Services tab. Make sure the Windows Firewall is turned off at the server and the client. Then restart the Service. Note: You should only be running one NLM on your network.
Make sure you can ping the NLM server by name at the client machine. You may also want to double-check your LICPATH.LIC file in your application root and verify that the hostname and the MAC address of the NLM are correct. If you have a system environment variable set, you should check that too.
If your NLM is installed on a Windows XP Professional, you should be aware that there is a limit of 10 concurrent network connections. Therefore if more than 10 network connections are made to your workstation, then all other connections will be denied. It is best to put the NLM on a Server operating system.
At the time of this post, the latest version of the NLM is 10.8.
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