Hello,
Sorry to hear you are having issues. There should not be any key required to activate if you purchase through steam.
Please try this.
1) Do the purge. Use this steps : https://forums.stardock.com/486084/fences-support-faq#reinstalling
but do not do the install part yet.
After you run the purge, reboot, look in Steam to see if there is still an uninstall option:
https://cdn.stardock.us/support/uploads/2018-09-20_09-44-07.png
If so, use it.
After, make sure no Fences directory exists here:
C:\Program Files (x86)\Stardock
If so, delete it.
After, make sure no Fences directory exists here:
C:\ProgramData\Stardock (note that that is ProgramData not Program Files (x86) )
If so, delete it as well.
After reinstall from Steam and Steam only, it should not ask you for a key. If it does try this again:
https://forums.stardock.com/486311/Accounts-and-Activation-Support-FAQ#steamkey
You absolutely should have sassteam.exe if you only have the Steam version installed.
Try that and let us know.
Thank you.
Basj,
Stardock Community Assistant.