From the error code I can see it is a Logic or its equivalent not an Icos. The L2 or F2 means ignition or frame failure, need to check a few things, so you need a boiler repair man, or call Ideal fixed price repair.I think they are all the same apart from kw rating (most have same parts apparently) it is the Heat 15 and the error code is L2 or F2 it comes up with one or the other once it decides not to fire. Restart and it could go straight away.
As it is intermittent, so better to wait for it to become persistent.