Steam has finally helped us find a solution to the problem that was preventing players who already had the beta version of the game from purchasing the full version, so preorder should now work for everyone. Hooray!
Here’s the link to the store page: http://store.steampowered.com/app/209080/
When you visit the game page you may still see the green banner saying that you already have the game, but you can ignore that. If you add one of the preorder packs to your cart, you will now have the option to purchase it for yourself, and the transaction should be able to complete normally.
Sorry to everyone who experienced problems and confusion trying to preorder, and thanks for sticking with us while we worked it out with Steam. We really appreciate your patience and support! If there are any further issues, please let us know — otherwise, store’s open! 🙂