Since you have got the igniter spaced properly that is probably OK. (must be no wider than 1/8" use a drill bit to check gap) Mine would light first thing in the morning, complete the heat cycle, and when the thermostat called for heat the second time, the furnace would blow, not light, go into shut down with a no-flame sense code. Led on the board blinking 3 times if I remember right. You can see the LED on the board by removing the outer furnace cover.
About noon, after several resets it would light one more time and then was done for the day. Next morning worked perfect first time, then no more.
I tried both tanks, looked at temperature, removed the 30lb regulator, replaced the 30lb regulator, and nothing seemed to affect it.
I bought a LP pressure gauge off Ebay and hooked it up to the furnace and watched it. It stayed @ 8.5" sometimes it would light, sometimes not. Since a crossover regulator is only about $30-40 I decided to try adjusting mine. Remove the black screw on cap and under it is a adjusting screw that will increase spring pressure, which increases LP pressure. 4 turns it bottomed out, pressure went to 10.5" and furnace started working just fine.
The stove, frig, hot water heater all worked fine on the 8.5" but not the furnace.
I found a like new (gauge) used one on Ebay, figuring the $50 was easier than to keep having the mobile guy come out plus it was a tool I did not have. The mobile guy had one, just not on his truck.
The board is usually it works or it does not. Igniter is a piece of wire and unless it is gaped wrong or the insulator is cracked it works. Voltage to the board must be at least 12vdc, ck ground. Sail switch usually works. See what your fault code is on the board when it does not light.
This is the type gauge I bought, there are several brands, and you can buy them at any place that has LP or home furnace parts.
Stay warm, Jim