Your gas water heater is not igniting for a reason somewhere along the fuel or ignition path, so work through it methodically.
Confirm the gas supply valve is fully open and that other gas appliances in the home still work, which quickly rules out a utility outage or an empty propane tank.
Check that the control knob is set to the on position rather than pilot or off.
On modern units with electronic ignition, a dead igniter, a failed piezo striker, or a tripped thermal cutoff switch will prevent startup, and the status light usually blinks a diagnostic code you can match to the label.
Blocked air intake screens starve the burner of oxygen and are a frequent cause on sealed-combustion models.
A blocked flue, failed gas valve, or contaminated burner assembly also stops ignition entirely. Call a licensed professional for any gas component replacement.
