Economite Conversion Burner - Winter Startup Trouble

I have an Economite Conversion Burner Model E20A unit on a Weil-McLain boiler.
I turned on the thermostat for the first time this season. I just hear an uninterrupted buzz and the burner doesn't ignite. I can hear the pilot light when the thermostat is off (without the buzzing sound).
Any thoughts on what might be going on would be greatly appreciated.

The gas valve may need to be replaced...the troubleshooting section of the manual should give some hints.