Your boiler is currently set to a manual testing mode used by engineers and is not following its normal heating schedule.

DIY fix possible

Locate the 'Chimney Sweep' button (marked with a small basket or chimney icon) on the control panel.Press and hold the button for at least 3 to 5 seconds until the display returns to the normal temperature reading.The 208 code should disappear and the boiler should resume its usual operation.