Ah ok, my mistake. Product code is not needed if you selected „Not Listed“. Just press Installing -> Next -> Not Listed -> View detailed Information, then check if there’s a potential issue/s detected.
Then try again with spacedesk installer.
By the way, can you answer some of our questions here:
1. Is this the first time you install spacedesk? Or you have previous version before?
2. Are you using an Administrator user account?
3. Were you able to install other msi installer aside from sppacedesk?
Can you please also try some workarounds suggested here: https://thegeekpage.com/installation-ended-prematurely/