There are a few reasons why this error can occur:
1) The DAEMON line in your license.dat file is incorrect or missing.
For license server, the DAEMON line should read:
Windows
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DAEMON MLM $MATLAB\etc\win{32|64}\mlm.exe ($MATLAB\flexlm\mlm.exe for releases prior to R2010b on Windows)
(where $MATLAB is the MATLAB installation directory)
Linux/Mac
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DAEMON MLM $MATLAB/etc/glnx{86|a64}/MLM
(where $MATLAB is the MATLAB installation directory)
(NOTE: prior to R2011a, the DAEMON line on Linux/Mac was "DAEMON MLM $MATLAB/etc/glnx{86|a64}/lm_matlab")
NOTE: Once you have made changes to your license file, be sure to restart the network license manager for these changes to take effect. For more information on how to restart the license manager, see the Related Solution listed below.
2) The SERVER line in the license.dat file on a client does not match the license.dat file on the server.
If you are running MATLAB using a concurrent license and you are on a client machine, make sure the SERVER line in your license.dat file matches that of the license.dat file on your license server.
The license file on the client machine varies depending upon operating system and version. For R2008a and above, the license file is generally called network.lic and is located in $MATLAB\licenses (where $MATLAB is the MATLAB installation directory). For versions prior to R2008a, the license file will generally be the following:
Windows
---------
$MATLAB\bin\win32 (for 32-bit MATLAB)
$MATLAB\bin\win64 (for 64-bit MATLAB)
Linux/Unix/Mac
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(where $MATLAB is the MATLAB installation directory)
The license.dat file on the server machine is located in:
$MATLABROOT/etc ($MATLAB\flexlm for releases prior to R2010b on Windows)
(where $MATLAB is the MATLAB installation directory)
3) The TCP port number used to communicate with the license server is already being used by another application.
For more information on finding an open port, see the Related Solution listed below .
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