What I've noticed in looking at Copa's Z class in ExpertFlyer is that it seems to always show zero availability, at least on the flights I've been on in the past three months. I've seen this over a week in advance, and even just in the days before a flight.

But, I'm 18/18 so far on upgrades under the ConnectMiles program, so it doesn't seem to be an issue. Sometimes, I've gotten upgrade notice 72 hrs in advance (I've got Platinum status), but other times it's barely over 24 hrs. I haven't figured out yet how Copa manages this inventory.