do you main the main website at vintagestory.at or account.vintagestory.at? for the former you can redeem an account when logging in on the latter
So if you are looking to download the game you have to do that on https://account.vintagestory.at/
The account on vintagestory.at is when you want to write on the forums or make more purchases.
You need a forum account to login to the website, it doesn't use the same email/password you use to play the game https://www.vintagestory.at/register