If you are noticing the following error message;

When first switching on your till terminal throwing up the error message; 'Error opening data source!'

The first thing to check to confirm the 'SQL Server (Fidelity)' is running which can be found under services.msc. If you click on your Windows Start and in the search area if you start typing services.msc using the on-screen keyboard or if you've plugged a keyboard into your till terminal.

This will open up the services.msc and if you look for 'SQL Server (Fidelity)' as follows;

In my example, the reason GPOS is not starting is due to the 'SQL Server (Fidelity)' has failed to start on bootup as you can see it's showing the service has not automatically started.

In the top left-hand corner if you click on the 'Start' option as screenshot 1.5.

You will see windows restart the SQL Service again.

Once started will look like the following as in screenshot 1.7;