Webstore, Matlab error "The maximum number of users for Toolbox has be reached"

Why do I receive an error saying "The maximum number of users for Curve_Fitting_Toolbox has be reached"?

The Curve Fitting toolbox is one of the limited availability toolboxes included with the University's MATLAB concurrent licenses. A list of unlimited and limited toolboxes can be found in the description section for the MATLAB offer on WebStore. If you get this message it means that all available licenses for this toolbox are in use. Unfortunately, a waiting list or notification is not available so you will need to keep trying. Eventually a license should become available as others stop using it. Alternatively, you can purchase a reserved seat for the Toolbox for an average cost of $200.  Please contact webstore@illinois.edu  if you would like to purchase one.