Your boiler has been left in a manual testing mode, usually used by engineers during a service, which is preventing it from running normally.

DIY fix possible

Locate the small selector switch or white dial on the front control panel.Ensure the switch is turned back to the 'OFF' or 'MIN' position rather than the 'Service' or 'Chimney' icon.Press the Reset button for five seconds to see if the flashing light clears.