After installation of COMSOL, the Matlab path may be changed, for instance after update or re-installation. Now if you run COMOSOL with Matlab, there will be an error, or sth like that:
To get COMSOL updated, go and edit comsol.opts, located in the COMSOL_FOLDERBin, change the string to the right path where Matlab is installed:
Close the file and re-run. Success!