Your boiler is trying to start the flame but the spark system isn't working correctly, preventing it from firing up.

Ignition trial period; check for mains voltage on Board 37 terminals for the spark generator

What causes this fault?

This fault occurs when the boiler's internal computer signals for a fire to start, but no spark is physically produced to light the gas. The most common reason is that the spark generator has failed electrically or the ignition electrodes have become worn or covered in carbon soot. In some cases, the control board may simply be failing to send the necessary power to the ignition system.