After activation, sig files are created here:
C:\ProgramData\Stardock[app in question]
You can watch this happen in real-time (activate and it will show up).
What can break this is if someone thinks they can just move those activation files \ restore from backup after a reinstall of Windows or substantial change to the PC (new motherboard for example).
The normal fix it to delete the sigs that are there and reactivate. If the app asks you again at a later date, no doubt if you go back to where they are stored, they are missing. Nearly every time that happens it's some AV\Malware app nuking the sig file.
Stardock Support Manager