I had a similar problem with my stove shortly after we purchased the camper. Under warranty (with another problem), I took it back to the dealer, I asked them to look at the spark on the stove. They didn't find anything wrong. It worked perfect. We even went out to the camper and the repair guy showed me. OK. Convinced me! Must have just been a loose wire.
Got the camper home and tried again! The one burner did not ignite! ARR!
Move past our first year of ownership, and now out of warranty. We don't use the stove very much. We fix stuff outside. But this one time we wanted to use the stove inside. And you guessed it ... no ignition!
Well, I decided it was tear something up or die time!
I looked everything over very carefully and then I finally caught it! The one wire from the knob to the burner that wasn't igniting? Cracks! Several of them! Cracks in the plastic coating on the wire. When the wire was laying on the bottom, the spark was striking at the crack, not at the burner.
Simple fix! I wrapped the cracks (I found 3 of them) with electrical tape, and it's been working fine ever since! 2 more years since then, and never a miss-fire again!
Check the actual wires from the knob to the burner. Make sure they have no cracks in the plastic cover! That is most likely your problem, especially since one burner works and another one does not.