Performed furnace diagnostic on Rheem system. Upon diagnostic found that system was not sensing flame at circuit board. Prior to this flame sensor was replaced with new one, Although still experiencing lockout due to no flame being detected. Found the polarity is reversed at breaker causing flame sensor inability to sense flame. Due to the reverse polarity this has caused damage to the circuitboard. Replaced circuitboard and corrected polarity at system and system is fully operational and heating upon departure.