Keep getting code 10, no blockages in venting,

Remove the top trim piece where the filter is. Disconnect the Gray flex hose from the vent terminal. Fire up the heater. If it fires you have either a blockage in the vent or a slow combustion blower. If it still gives you an error code, Inspect the combustion chamber for cob webs or debris. You can access the chamber by carefully pulling the flame rod and electrode out from the front port. Be careful with the fiber gasket. Blow some air in the chamber and vac out what you can. Polish the flame rod with a tooth brush and clean off terminals on electrode.