Troubleshoot Rheem Furnace Package Unit 5 blinks 3 blinks

Rheem Furnace troubleshoot why it won’t run. Cleaning the tubes, flame rollout switch, vacuum switch and squirrel fan. Codes with 5 blinks on board and 3 blinks on board. 5 was the flame roll out switch and three was the thermocouple that detects heat on the last jet. Also this video talks about the pressure switch and what it does even though it was previously replaced.