If the EFTPOS machine says it needs to logon, you'll need to go to the machine the actual EFTPOS machine is connected to and click the up arrow for the tray on the task bar and you'll find the S, C, C icons. if the green C icon shown below is yellow, there is a problem, restart the computer and give it time for the apps to start up again.
Once you can see the green C double click on the icon and the Linkly Client GUI will show up, click on Ctrl Panel... button
On the EFTPOS Control Panel page click the Logon button and it will have windows to show it is logging on. Once it's logged on, the machine should work.