This is the #1 cause. AspenTech uses Sentinel RMS (formerly known as LSF – License Service Framework). This service must be active on the (for network licenses) or on your local machine (for local licenses).
You start by checking the license manager, FlexLM, to see if there are any issues. You navigate to the FlexLM license server and see that it's running, but there are no available licenses for Aspen Hysys. You suspect that there might be a problem with the license file or the server configuration. Aspen Hysys License Checkout Failed