Have tried removing the car's vacuum supply from the process? It's possible that when everything is installed correctly due to other demands that there just isn't enough pull on the lines to move the actuators.

I've got a similar problem in my coupe with the vacuum controlled seat back locks - they only lock when I put the ACC into defrost mode because (I think) there's a minor leak somewhere on one of the flap door actuators. Similar behavior - they tested perfectly in isolation, but not when connected to everything else. I can use my ACC as a "seat lock button" - I select defrost and I can watch the pax seat actuator move. The check valve on the seat back line stops them from unlocking when not in defrost.

Try a very short test run using Mity-Vac connected to the switch then connected to the lights. It should pull the lights up and hold them in the 0 position, maybe hold them in a lower position or slowly drop them in 1 or 2 (as the vacuum 'leaks' from the switch - but you might be able to hold them up with slow pumping) and it should drop them in the 3 position. This may test your components and isolate the problem at the supply.

--Edit-- watch the pressure gauge on the Mity-Vac for bleed down. You may have to block the vent hole on the switch after changing selections, or maybe use the "brake bleed" kit as a mini reservoir so you don't immediately dump all vacuum when going from 0 to 1, 2, etc. --End edit--

If nothing else this may give you a data point of how much vacuum you need on the actuators to pull them up. Then you may need to start troubleshooting to eliminate enough leaks on your accessory line or select a supply point that consistently provides that much vacuum.

Or install everything and select defrost? It works for me!