It's an old question, but the answer could help someone. I had the same problem with a standalone app that was installed in more than 50 computers and it made deal with three causes:
(1) Windows firewall has blocked service (perhaps due to an update of the Windows itself or a new network policy), so you have to unblock;
(2) An old version of Windows, so you have to update it; or
(3) Matlab Runtime crashed and you have to reinstall it.
