Can you "see" a spark at the first burner?
Make sure the burner is clean. The electric must make an ARCH between the ignitor and the metal surface of the burner. Clean the orifices with a toothpick, to ensure the gas is coming out the holes near the ignitor.
Does the BEND on the ignitor LOOK like the ignitor on the back two burners? Sometimes, cleaning causes the little probe on the end of the ignitor to be bent outward. If that little probe (I have no idea what they actually call that part of an ignitor)is bent to far away from the metal surface of the burner, you will not get a spark.
If the burner is clean, and the ignitor looks like the other ones that are working.....and you didn't somehow disconnect the wire to that ignitor...than it sounds as if you need a new ignitor.
Pretty simple swap..
