This is usually due to Windows conflicting with Final Draft. To get around the issue:
1. Close Final Draft 13.
2. Reboot the PC.
3. Go to your Start menu (the Windows icon in the bottom left corner of your screen)
4. Right-click on the Final Draft 13 icon and click "Run As Administrator."
5. Once Final Draft 13 has reopened, go to Help > Check For Updates.