Add C wire to Argo AR821-T

[Frederick]

I searched for this topic, and while a few similar questions came up, none of the responses appear to work for me. I have a 30-year old Peerless boiler with 3 zones. In order to add a Ecobee thermostats, I have to add a common wire to all zones.
The thermostat relay (an Argo AR821-T) has a 24V transformer, and measuring between T and P (red wire and the closest P terminal) I get ~30V. When I hook up a wire and feed it to the C terminal on my thermostat however, nothing happens. I tried attaching it to the other P terminal as well, which makes no difference. What am I missing?

 

[Stuff]

You likely need to swap the red and white wires.
For that unit R is on the left, W is next to it, then another R, then C on the far right.

 

[Sponsor]

 

[Frederick]

That was dead on Stuff! Thank you so much, everything works now!