Same problem for me.
I played a multiplayer game, so the password was working, then I crashed and it wouldn't let me log back in.
To try and correct this issue I:
* Rebooted
* uninstalled/re-installed Demigod
* Deleted the stardock dir under Appdata
* Reset the password (works on the website, stored in pw manager, so not a typo issue)
* Tried a simple password with no special characters
* Tried using my username instead of email address, even though that had worked fine
* Let it cooldown for 24 hours
* Tried a european vpn
Not sure what else to try at this point.