Well, the game is licensed to the first owner... and since sins have no real DRM, game remain licensed to the first owner who can always use Impulse for upgrade and Icon for online game...
In the past, there have be a very few case where transfer was possible... when both the old owner and new owner have contact the sales department from Stardock...
In some very very rare case, the new owner was allowed to purchase a new key at reduced price...
If you have buy the second hand version in a shop, simply return it and ask a refund... they have sold you a product who cannot work... if you are located in a European country, you have 7 days for claim a refund... if you are from US, chance is that you will not have a refund...
Problem is that due to the lack of protection, your second hand Sins Of Solar Empire may as well be a pirated copy. Will be very difficult to prove that you are a honest guy...
