Hi it does sound like the air pressure switch is not pulling in to operate the ignition, if you say the fan is working the next thing is the air pressure switch should pull in, it can be a blocked ventura or cracked pipes to it
It needs checking out properly and so does the p c b its not a job for the d i y as it involves removing the combustion chamber cover and that is a no go area
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local