If the blower is functioning ( ordinarily the blower will come on for a time before ignition, if the board is not getting a signal from the sail switch that the blower is functioning it will enter a shut down sequence). The function of the sail switch is to tell the board the blower is functioning. If you can access the sail switch short the leads and if it runs, the switch itself is the culprit. Otherwise, it's highly likely it's the board. You might try removing the board and spraying it and the plug ins with something like WD40 fast drying contact cleaner.
