This has probably been mentioned before, but the only thing that ended up working for me was manual activation, after numerous emails to tech support.
Go to this webpage for instructions:
make sure when you enter your serial number that's it's all caps (at least, that's what it needed from me). I didn't receive any notification but the next day Stardock Central said my game was registered and I was able to fully use and update it. Hopefully this will help someone.