When an Individual license of ExtendSim is activated, it creates a license file (extendsim.lic) that is stored by default in the end user's Documents\ExtendSim folder. If that license file becomes inaccessible, ExtendSim will not launch but will instead give this error message and perhaps revoke the license.

The three most common reasons why the license file would suddenly not be accessible to ExtendSim are:

• The license file got deleted. This can happen if the device is "swept" and any files that were created after installation get removed. The fix is to set the sweep such that it does not remove any .lic files.
• The license file is modified, such as being changed to "extendsim.lic.bak". This can happen if the ExtendSim folder containing the license file was stored in the cloud (for example, on OneDrive or DropBox) and then used to replace the ExtendSim folder on a device that has a different license. There is no need to store the files that ship with ExtendSim in the cloud. For OneDrive, you can exclude the license file or the ExtendSim folder from being synced with your device.
• You try to launch ExtendSim by double-clicking a model file that is stored externally, such as in OneDrive, DropBox, or a portal, and that model file is shared with other ExtendSim licenses. Instead, copy the model file from the external source to your local device. To open the model file, either:
  • From within ExtendSim, choose File > Open and browse to the model's saved location to open it.
  • Right-click on the model file icon on your device. Choose Opens with... from its properties and select your ExtendSim installation. Then, you can double-click the model file icon itself and it will find and open ExtendSim.