Upon arrival spoke with customer. 1st floor system is not operating. Customer tried to reset system @ emergency shut-off switch. System still would not run. Check control board to see error code E276 which relates to a soft lock from number of tries exceeding maximum limit. System will also give error code E274 and E228 relating to pressure switch or limit switch. All safety switch was checked @ this time. Continuity test on High limit and resettable limit. Checked pressure. Pressure switch would close to complete sequence of operation where igniter will glow but furnace would not fire. Checked and confirmed that gas valve is getting 24volts. Checked resistance value @ hot surface igniter. Clean flame rod flame sensor. Ran and tested system operation once more. Furnace tries to fire multiple times but would not ignite after glowing of hsf indicating a bad gas valve. Customer is aware that gas valve needs to be replaced but there could also be an issue with pressure switch. Office to fo