If you're using Internet Explorer, this is typically caused by the sign on page being in a different security zone from your ClientTrack application. The authentication cookie cannot be passed between zones. You can see the current security zone by looking at your status bar at the bottom of your browser window.

To resolve this issue, open the Tools menu and choose Internet Options then choose the Security tab. Select the Trusted sites zone then click the Sites button. In your list of trusted sites, add both https://www.clienttrack.net and https://usw.clienttrack.net. Click the Close button to close the trusted sites dialog, then click OK to close internet options. You should now be able to sign in.