It should prompt you for a username and password as long as you have configured your proxy server settings. Click here for notes on the Proxy Server settings. This is a generic error from the proxy server, that in almost all cases means that the proxy server is blocking outgoing and incoming requests on port 13. Ask the site networking adminstrator to unblock port 13 in the proxy server restrictions. A proxy server acts as a security agent, allowing only authorized requests to pass through a firewall.
Most work environments use a proxy server of one form or another.
You have enabled an Update Interval option which means AtomTime98 is now running in the background. You should notice an AtomTime icon in the System Tray area. When using one of the Update Interval settings, the X button simply closes the display but leaves the application running in the System Tray. If you want to exit AtomTime98, either click on the Exit button or right click on the System Tray icon and pick Exit from the menu. I changed some setting and now when I start AtomTime98 it seems to do something then exit.