You are getting this error because the libstdc++.so.6 file is not linked to the actual library that it is supposed to be a symlink for. This file needs to link to the library to correctly start the MLM on the network license manager.
For different reasons the symlink can sometimes not be created correctly, so to resolve this we need to manually create the symlink.
To create the symlink we need to go to the directory that the file it is referring to is located in, the directory should be:
(Where $MATLAB is the installation directory of MATLAB)
Inside of this folder you should see:
libstdc++.so.6.0.17 (version number may be different depending on the release of MATLAB)
The libstdc++.so.6.0.17 is the actual library, while the libstdc++.so.6 is currently the empty file that should be the symlink for this library. To resolve the issue run this function inside of your terminal window:
ln -sf libstdc++.so.6.0.17 libstdc++.so.6
This will create a symlink over the empty file.
NOTE: You may want to do this for any of the other libraries in case they had the same issue happen to them as well. IE: libquadmath.so.0 and libgfortran.so.3