Platform: All Platforms Versions: All versions

Problem Description

Any of the following errors can appear for example if the COMSOL application has problems communicating with the license manager:

License error: -15.  
Cannot connect to license server system.

License error: -96.  
License server machine is down or not responding.


This solution assumes that you are a fully qualified system administrator. Please contact your local system administrator or COMSOL license administrator if you are unsure how to proceed.

Below are solutions for the most common license errors. For a complete list of similar errors and workarounds, please refer to the section Troubleshooting License Errors in the Installation and Operations Guide, available at

First, identify the exact FlexNet error code (highlighted in red in the image below):

Use these links to go to the corresponding solution:
FlexNet Licensing error:-15,570
FlexNet Licensing error:-96,491
FlexNet Licensing error:-15,10032
FlexNet Licensing error:-96,7
FlexNet Licensing error:-15,10

Firewall Problems

When the detailed FlexNet error message is

FlexNet Licensing error:-15,570.


FlexNet Licensing error:-96,491.

The license error is most likely caused by an active firewall that is blocking the license checkout attempt.

Check if a firewall on the license server is preventing the connection from the COMSOL client computer to the license manager. If there is an active firewall required on the computer on which you run the COMSOL license manager, make exceptions for the license manager processes by configuring the firewall as described below.

Configuring the Firewall

At least two port numbers must be opened up in the license server's firewall to allow client computers to connect to the COMSOL license manager. The top three lines in a license.dat for a COMSOL license manager look like this:

SERVER my_server 123456789ABC 1718

The license file above specifies that TCP port numbers 1718 and 1719 (the default port numbers) will be used by the lmgrd and LMCOMSOL processes respectively. You may change them to any free port number, but you must restart the license manager for the changes to take effect.

Configure your firewall to allow incoming TCP connections to the chosen port numbers. If you are unsure which port numbers are free, or how to allow firewall access to them, please contact your system administrator.

A solution that may be less secure, and therefore less recommended, is to configure the firewall to allow access to the lmgrd and LMCOMSOL executables on all port numbers. In this case you do not need to modify the license.dat file.

For more information, see the menu Help->Documentation and find the FlexNet Documentation.

Connection or Settings Problems

If the detailed error message contains the string

FlexNet Licensing error:-15,10032.

For Floating Network Licenses (FNL), Class Kit Licenses (CKL) and COMSOL Server Licenses (CSL), this usually means one of two things:

  1. There is something, most likely a firewall, blocking the computer where you are trying to start COMSOL from accessing the license server on the ports that the license manager is using (by default 1718 and 1719). This can happen if there are some internal requirements, for instance a requirement of either direct or VPN connection to the internal network where the COMSOL license manager is installed.
  2. The ports given in the local file are not the ones that the license manager actually is using. This can happen if the license manager uses other ports than the default ones.

To investigate if you can connect to the license server computer on the specific ports the license manager is using, please see this entry.

Wrong Hostname in License file

If the detailed error message contains the string

FlexNet Licensing error:-96,7.

chances are that the computer with the hostname specified in the license file is not available.

  1. Check that the license.dat file on the COMSOL client computer points to the correct license server hostname. First, find the license.dat file in the COMSOL application folder:
    Windows: C:\Program files\COMSOL\COMSOL60\Multiphysics\license\license.dat
    Linux: /usr/local/comsol60/multiphysics/license/license.dat
    macOS: /Applications/COMSOL60/Multiphysics/license/license.dat

  2. Check that the first line has the correct license-server hostname. For example, if your license server hostname is mylicserver, the first row in the license.dat file should look like this:

    SERVER mylicserver 000123456789 1718

  3. If the COMSOL client computer does not recognize mylicserver as a proper hostname, it might help to instead use the fully qualified domain name ( or the IP address. If neither of these works, there might be a problem with DNS or the HOSTS file on the client. Please ask your system administrator for advice on how to connect with TCP/IP to the license server.

License Manager not Started

If the detailed error message contains the string

FlexNet Licensing error:-15,10.

the license manager is not running on the license server. Install and start the license manager according to the instructions in the Installation and Operations Guide, available at

Find More Information

If the problems remain, please contact and include the license manager log file. The log file is placed on the license server computer, usually at this location:

Windows: C:\ProgramData\COMSOL\comsol60.log
Linux and macOS: /var/tmp/comsol60.log

NOTE: The log file is created by the license manager after it has been started.

See Also

Solution 1022
Solution 1078