Charlie,
Before you start pulling hair out and definitely before you spend any real money, check the LP system pressure.
You need:
Some clear tubing that can fit over a stove burner jet
A yard stick
Rubber bands - at least 2
Use the rubber bands to hold the tubing to the yard stick. Put some water in the tubing. You just made a manometer to measure low pressures.
Push the tubing onto a burner jet and turn the burner on.
The water should shift. The difference between the two levels should be 11". You can probably adjust this at the regulator. If the regulator is more than 10 years old, consider replacing it.
Matt