If the sign-in process for the admin dashboard fails, you may need to check your organisation's firewall.
The Citizen sign-in app uses WSS (Secure WebSockets) to access the admin dashboard.
In some organisations, you may find that your firewall or proxy does not 'upgrade' the SSL connection to WSS, and automatically closes the connection.
This is easily rectified by ensuring that your SSL endpoint accepts WSS.
There is a simple test available here to check your ability to receive WebSockets. Check that this Secure WebSockets test passes if you are experiencing issues.
This is a common issue with WSS - for deeper information, Stack Overflow has more information here.