I’m sorry that you had trouble. The Dark Planet trial should automatically start it’s 30 day trial when you install it, there is not a trial activation code for it. If your SeL was damaged that could cause the trial not to work.
Please update to the 1.1 from http://www.steinberg.net/index.php?id=downloads_vsti_dark_planet&L=1
Now when you attempt to load Dark Planet in Cubase, do you get an error? If so, I would suggest contacting your local support so they can help you reset the licensing.