Any heating and cooling Guys out there? I have a question

Ceramic only for a HSI system, his is a spark ignition, as well, correct there are many safety situations such as Vacuum switch, roll out switch, flame rod, vent switch etc. But considering that the furnace attempts to light tells me all these safeties are being met and the gas valve is opening. It would not try to fire if any of the safeties are not satisfied. These are wired in a series one locked out or not functioning and it would not fire. Trouble shooting skills 101. Its sparks , it lights...doesn't stay lit, so all else is good, it will be flame sensor seeing no flame after being lit (mili seconds after) or back to the board where this is all times out via PC board. Yes, never bypass any safeties on the furnace except for trouble shooting, never leave a safety bypassed.