Hello, it turns out I’ve bought Gratuitous Space Battles about 5x with all the indie bundles I have.
My original purchase was the collectors edition through steam. I don’t see a multiplayer key there when I look, so I decided to try one of the others I had (through the humble bundle).
The key was accepted but when I tried to pick my username, it said it existed already, which made me think that I might be able to reclaim my existing profile. Is that possible?
Thanks.
If I recall correctly, so long as you can remember which one of the 5 keys you used with that user name, then yes, you should be able to reclaim that account.
I think my original one was purchased off of Steam, and it looks like the code from it does not work or is in the wrong format. 
Hmm, well, 1 down - 4 to go 
If that fails, might i suggest for you to send a PM to Cliffski and include your user name, email address you used for the purchase and the 5 keys you have.
Maybe he can interigate the Positech server and see which one you need.