Problem Description

I have a CPU-Locked License (CPU) or a Named Single-User License (NSL) installed on a Linux machine and get an error message dialog box containing the phrase:
Licensed number of users already reached

The detailed error message displayed by COMSOL:

Could not obtain license for COMSOL Multiphysics GUI.  
License error: -4.  
Licensed number of users already reached.  
Feature:     COMSOLGUI  
License path: .../license/license.dat...  
FlexNet Licensing error: -4,132 

Solution

If you are a Floating Network License (FNL) user, please refer to Knowledge Base 1059.

For CPU & NSL licenses on Linux computers, a license manager is used and this error can be triggered when trying to launch several COMSOL sessions simultaneously.

If you want to run multiple COMSOL sessions simultaneously on a Linux computer, they have to be started from the same terminal window. You can do that by adding an "&" at the end of the "comsol" start command in order to keep the terminal window active after the first session has launched.

Running

comsol &
comsol &

from the same terminal will start two COMSOL sessions without triggering the error.