Hey, I have _exactly_ the same issue as xTRICKYxx did in that other thread that got locked (before anyone posted a solution!!). He summed the problem up pretty well, so I'll paste the relevant part;

"

After downloading, I get a prompt by this window called 'Stardock Account Registration'. There are 3 boxes I need to fill out: Stardock Account Email, Password, and Serial. I obtain my serial by right-clicking the game on Steam to view the key. I already had a Stardock account Email. 

So, I fill those boxes out and I have to options: Quit and Register. I click Register, NOTHING happens at all. No error, no spinning wheel or any network activity from the program; nothing happens. 

I have tried running the program in Compatibility mode, allowed the program through my firewall, made up random information, NOTHING. I also can make a new account in the program and clicking register through that only makes the program flicker. 

"

That's exactly what I'm experiencing. I paid for the game through steam, downloaded and installed, activation screen on run, form filled out, been a stardock customer for years, nothing thereafter. Instead of trying to help anyone, you guys locked that perfectly valid thread after removing the offending post - seems redundant to me.