For a unpowered sensor (like a wired magnetic reed-type door/window contact sensor), use the S1 / C (and/or S2 / C) slot, not the C/VC slots.
Using the "Contact Sensor" attribute for those currently results in a backwards open/close status - based on posts earlier in this thread, it sounds like Zooz is going to fix that in an upcoming firmware release (hopefully soon!!)
ETA - some setup-related info here (from a Zen16 thread where Zooz first mentioned they were realeasing the Zen17): New Zooz ZEN16 Multirelay
