This can happen following a major Windows update.
The PowerDesk 9 serial number is actually still valid.
Please uninstall the program using the control panel in Windows, and then restart Windows.
Next, download and save this file. This is the installer for the latest update for PowerDesk 9.
Go to where you saved PowerDesk9_setup_signed.exe, right click on it, and choose Run as Administrator.
This will reinstall the program. Use the same PowerDesk 9 serial number as before.