Contact your IT department to verify that your account permits ActiveSync Connections.
Further Information:
The server may have policies which prevents you from using ActiveSync. AstraSync supports ActiveSync version 2.5 and 12.0. If your server requires 12.1 and later policies, AstraSync may not work correctly.
Information about ActiveSync Policies can be found within http://forum.astrasync.com/Default.aspx?g=posts&t=86