Hi.
That link will help if you currently have the game installed with a valid key, I believe.
I assume that you didn't register your key in your online profile on this site (as you don't seem to have registered on this site previously).
Probably the only other thing you can do is to contact info@shipsim.com and explain what has happened. Presumably you have some evidence that you purchased the game (receipt etc). If you have that, then you can at least ask them.