baxi solo wm 40/4pf - won't light?

Hi
I have a boiler problem that is proving perplexing.
It wouldn't fire up so I worked with the fault finding chart and couldn't see the pilot flame so replaced the controller board as suggested - no change but I did notice that there was (and probably had been) a pilot flame but I needed to look to the side and down to see it.

More with the fault finder and I found that there was power to the main gas valve but the valve wasn't operating - so I changed the valve.

This appeared to fix it but over the next week the boiler failed to come on some mornings before stopping altogether.

Now - after another fault finding session I can see that the pilot is on and apparently a good flame but the controller is still sparking and the main gas valve is not receiving power.

The fault finder suggests a faulty board - but it is a new one (unfortunately I do not still have the original).

Can anyone suggest any reason why the main gas valve is not getting a signal - the boiler does not have a thermocouple and I cannot see anything that could be telling the controller that the pilot is alight.

Very perplexed and cold!