Windows Security flags the Thunder program as containing a virus or is unwanted software. As a result you are unable to launch the app.
1. In the search bar in the bottom left near the Start button, search for Windows Security. Once this is open look for Settings in the bottom left of the window, there should be a gear icon by it as well.
2. Once you've opened Settings, look for Protection History. In this protection history you should see the event where Windows Security put the Thunder program into quarantine while waiting on your action. By default, Windows Security will say it's been removed but you can chose to allow or restore the program by clicking on the Actions drop down in the "Potentially Unwanted App Removed" history box.
3. Select 'Restore' and give the machine a chance to restore the software, it should take about 5 minutes. After it's been restored, attempt to launch Thunder again and you should be able to get in.