The LDK license is sensitive to changes in the system that can cause the service to disable the license. It usually happens the first thing in the morning when you start the system up. You will most likely see two errors.
Once you hit okay, you should see the next message.
These messages almost always point to the Sentinel Service needs a restart. Restarting is a simple process of opening the service window, navigating to the Sentinel Services, selecting that service, and restarting. I have step by step instructions below.
To restart the Sentinel LDK License Manager Service.
1. Open the Services. From the Start Menu, type in Services, and select it.
2. Browse to the Sentinel LDK License Manager, and select it. Once selected, click on 'Restart.' The Sentinel LDK License Manager service will now restart.
3. Open the LDK Tool to verify that the Sentinel LDK License Manager is working. You should see that there is a License in the Keys Window.