If you are trying to update Demigod via GameStop PC App (Impulse) and are unable to logon you would need to contact support through Gamestop. Or you can use the option in the GameStop PC App (Impulse) to retrieve your password (http://screencast.com/t/6oFWKQiZdFyR).
If you have an account with Stardock and your copy of Demigod is registered with us you can download the update from us via the My Account page on the Stardock store. Below are important links that can help you with your Stardock Account.
Create Stardock Account and register Demigod: https://services.stardock.net/accounts/createaccount.aspx
Register Only (if you already have a Stardock account): https://services.stardock.net/accounts/registerproduct.aspx
My Account Downloads Page on Stardock Store: https://store.stardock.com/myaccount/products
Reset Stardock Password: https://services.stardock.net/accounts/resetpassword.aspx
Note: In today's update there is a bug where saved passwords are failing. We are aware of the issue and will be issuing another update in the next couple of days to address the issue. If you are still having troubles logging into Demigod with your Stardock account, use one of the above links to assist you with logging in.