Can a Zone Valve problem prevent my Weil Mcclain hot water Boiler from firing?

One thermostat zone is working fine, opening the zone valve and firing the boiler. The other thermostat is opening its zone valve and I can hear the relay chattering like it normally does before it fires, but the boiler does not fire. Is the zone valve bad? Does the whole valve need to be replaced or is it maybe an actuator or end switch that can be swapped out?