A gas grill that won't light is almost always a clogged burner tube, a failed igniter, or a tripped regulator — not an empty propane tank.
Make sure the propane tank valve is fully open — counterclockwise until it stops. Then turn off all burner knobs, close the tank valve completely, disconnect the regulator, wait 30 seconds, reconnect it, and slowly reopen the tank valve. This resets the regulator's safety mechanism.
Press the igniter and listen for a click and look for a spark. If no spark, replace the battery or igniter module. Remove the grates and burner covers and inspect each burner tube for spider webs or debris. Run a pipe cleaner through each tube completely.
Make sure each burner tube is properly aligned over the gas orifice. Reassemble the grill, open the tank valve slowly, and try the igniter. If it still won't light with the igniter, hold a lit match near a burner and turn the knob to low to confirm gas flow.
Never use a gas grill indoors or in an enclosed space. If you smell gas and cannot identify the source, turn off the tank valve immediately and move away from the grill.