I had something similar. What worked for me was delete the folder under %appdata%, uninstall and reinstall the game. Load game (it will look like it didn't work) play through the intro until you get to the character screen with the new lvl0 char. Exit/log out of the game via the red door icon at the bottom of that screen, you will be taken to a screen with the giant 'sync' button in the middle. choose email option to sync/sign in if your game is older than nov23 (if you made your game dec23 or newer then and only then it's a steam log in) enter your details, sync and you should be back in your account.

When I was troubleshooting some people didn't have to go through the deleting folder and uninstall/reinstall, all they had to do was play through the intro, on the char screen log out, sync and then they got into their account (FYI)

If that doesn't work drop lava a email but lava only looks at emails on sunday.