g/w micron 40ff reset led on, burner led fast flashing?

Boiler not working & LED's on. Reset boiler, it will ignite then shut down. It does this three times then LED 1 Reset LED remains ON, Burner LED Fast Flashing (8Hz).
Fan runs Ok, C/H pump running, continuity check on ignitor & lead Ok.
System circa 10 yr old, PCB replaced 03/2007.
G/W tech advise could be ignitor / thermistor or PCB!
Any advice please?