the magic eye is named a photocell.
if you remove the red plastic cover from the burner, held on with 2 screws, the photocell is underneath it.
the cell looks like a 'spark plug cap' a thick black plastic plug with a lead moulded into it.
pull this out carefully, wiggling it, and wipe the end clear of any soot.
then replace it and try to fire boiler.
then book a service engineer as your co2 settings are way off and the burner needs calibrating to 12% co2 65c.