Well, "passive cooling" means that it requires no external power to cool. Doesn't necessarily mean it's normally plumbed into the circuit. Most probably it would not normally be, as the passive cooling would definitely decrease the power output (it is, after all, what it is designed to do).

So there was probably one or more valves that did not get switched, as the system somehow didn't think they needed to, due to something not being configured as they should.