If your operating system has recently been updated and you are using an ExtendSim release prior to 9.3, Windows may be blocking the launch. With release 1709 (October 2017) Windows changed how the memory manager worked, which caused crashing and hang ups when launching older installations of ExtendSim.

If you are using ExtendSim 9 (released prior to November 16, 2017), 8, or 7, get your fix here.

If you have a Network license and ExtendSim on Client devices no longer launches, the Service (exService) may not be running correctly. In cases where the Server has been restarted, exService sometimes fails to correctly re-communicate with Client devices. The solution is to Stop the Service on the Server, then Start the Service. (Note: A Client license of ExtendSim will remain launchable for several hours after losing communication with the Server’s License Manager. However, if communication is not restored, ExtendSim will not launch. Thus, this issue can occur many hours after the Server has been restarted.)