I have a Glowworm 100f gas boiler system
It has a fault where the ignition stays on when the pilot light is lit. So the main burner won't come on.
I went through the Gloworm fault-finding list and it said if this happens to change the P.C.board. I had the P.C board checked and the company who did it said it tested okay.

Gary Foster, October 2020

This may help.

http://www.ultimatehandyman.co.uk/forum1/viewtopic.php?t=23457

The ignition lead provides a high voltage / high current path for the sparking. It also provides a low voltage / low current path for the flame sensing, which needs to sense a flame before allowing the main burner to start. See where this is going? If the sparking and the main PCb are OK, then have a look at the ignition lead and all its connections and check for continutity.
Also check the electrode is correctly in the flame as per the manual (download or contact Glowworm if necessary)

ladskcnaslc, October 2020