Your boiler has detected a problem with its internal fan and has shut down as a safety precaution, meaning you will not have any heating or hot water.

Fan Fault.

What causes this fault?

This fault occurs when the boiler's control system can no longer communicate with or power the internal fan, which is responsible for clearing exhaust gases. The most common reasons are the fan motor seized due to wear and tear, or a communication failure between the fan and the main circuit board. Because the boiler cannot safely vent fumes without the fan running at the correct speed, it will shut down immediately.