Halstead ace HE 24 (combi boiler)?

Boiler is showing E. on the LED display, The fan is working if I turn temp dial to standby it shows 0 (no flashing) if I turn dial to reset it shows E. running hot tap in bathroom or kitchen has no effect ignighting boiler also water pump is working it just won't fire up it's an Halsted ACE HE 24 combi boiler gas is on and water pressure is above 1 bar can any one help me.