two-fold question about my radiant in-ceiling heat that doesn't work in two rooms.

One room has power going to the thermostat and the thermostat breaks continuity properly. I figure this means the heating elements are broken somehow.

The other room has no thermostat, just a bunch of wires that I can't seem to get voltage to. But then I remembered, they wouldn't show the line voltage if there was no load/circuit attached, right? i.e., the thermostat wasn't completing a circuit so no voltage. Complicating matters, I don't know if this box is actually for a thermostat or if there's heat in the room. There are four red wires, one white, and one black. The red wires are in 2 pair that are capped off with wire nuts.

But then, if the heating elements in the first room are broken, how are they presenting a load and showing the line voltage without producing heat?