Are you using MATLAB R2015b? There is a bug within MATLAB R2015b that affects the MATLAB Add-ons Explorer and Manager. When both the license manager or WLAN System Toolbox are installed in the same location as MATLAB it causes the Add-ons Explorer and Manager to load indefinitely.
or perform one of the two steps below: - Uninstall the license manager or WLAN System toolbox off the computer running MATLAB and install it on a different computer.
Or, if the license manager must be on the same machine. - Uninstall License Manager and install to a new location (that is not MATLABROOT).