What this means is that the connection between your Steam and Paradox account has expired. It's easy to fix though and all you need to do is the following.
- Click the error message on the account page
- All done!
OR, if you don't see the error message anymore:
- Login to your Paradox account at accounts.paradoxplaza.com
- Click Settings
- Click Disconnect for your Steam account
- Click Connect and follow the steps
- All done!