Im on vintagestory.at I already paid for the game and got an account sometime last year, I just wiped my browsers history yesterday so I needed to sign back in but like I said it just tells me my information is wrong.
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