(Err: 15) Unable to Connect to License Server

First of all, you should only be using a license server if you have a floating license, which most likely you do if you have a purchased license, but otherwise you probably do not. Second, the license server must naturally be configured and started, before you can connect to it. If you don’t actually have a license server, the solution to this problem is thus to change the license configuration to standalone. The easiest way to do this is to run the tool atk_license_config from a terminal window (Linux or Windows); on Windows you can also use the shortcut “ATK License Configuration Utility” in the Start Menu (under Programs>QuantumWise>Atomistix ToolKit X.X>Utilities). In the license configuration utility, follow the instructions to choose the “Standalone” option and specify the location of the license file. See the Installation Guide for more details on managing the client license configuration. If you do have a floating license, and a license server has been properly configured, the problem could simply be that the license server has been stopped; this is not least most likely the case if it used to work before, and now doesn’t. If so, restart the license server and try again. You can check for active license server on the network using the command lmxendutil -licstat which works on both Linux and Windows. It is also possible that the network connection between your computer and the license server is blocked by firewall rules.