Your boiler is currently running a maintenance program intended to purge air from the system after it was recently filled with water.

DIY fix possible

Wait for the filling program to complete automatically, which usually takes about 20 minutes.Ensure your heating controls are set to a demand state if the boiler does not exit the mode on its own.If the code persists after 30 minutes, switch the boiler off at the fused spur for one minute and turn it back on to reset.