[Kerbal Space Program] I bought the game on Steam, but I want it on the KSP Store/GOG as well.

If you bought the game on Steam, you will only have it on Steam. To get it in the KSP Store too, you will have to purchase it here. Do keep in mind that the Steam version is DRM free, so it can be played offline as well, so you’re really not missing out on anything with the Steam version instead of the KSP Store one.

If you're still having issues, please submit a support ticket here.