The application status page shows no current outage with the Add-On Explorer, and the most recent outage listed in the history occurred almost three weeks ago.
Please try the steps given in this Answers post (you may need some assistance or information from your IT department for some of those steps.) If they do not resolve the problem please contact Technical Support using the telephone icon in the upper-right corner of this page and work with them to determine what is preventing your MATLAB installation from downloading add-ons.
