Advanced Stove 1 Of The Burners On My Stove Doesn't Work?

1 of the burners on my stove doesn't work? - advanced stove

I have 4 burners on my stove and 3 of them give birth and gas, but left-back did not give all the gas and before him, anyone know why do it? In thinking podíanutilizarse blocked, but unfortunately I'm no expert, but if someone could me an idea of what .. it would be great

Thank you in advance:)