Call for heat no boiler fire???

I have a three zone very basic boiler system in my home. Two upstairs zones in one's own in the basement. The basement heating zone works perfect. I turn up the thermostat, moments later the boiler fires and all is well. The two upstairs zones are the issue. Whenever I turn either of them up calling for heat the zone valve opens but that is it. The sequence of operation stops there. The boiler never fires. I have the old antiquated tstats as pictured. The boiler also makes our hot domestic hot water and that zone too works perfect. I am hoping it is just a thermostats that need to be replaced. What would cause the zone valve to open up but not continue the firing sequence!? I am a master plumber but by no means a service guy. I run larger commercial projects. Can someone please give me some insight!!!?? I'd surely appreciate any and all help/advice!!

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