I am renting an apartment and the tenants recently complained about water droplets on the ceiling in one of the rooms. The apartment is on the first floor and surrounded by plants (we live in a tropical climate), and there is no history of water infiltration before. There are two other floors in the building, and neither apartment presents any water problems. The new tenants painted the whole apartment with Lanco Urethanizer, and since then the problem has appeared. We are currently in the middle of the rain season and hurricane season, but other than that, I have no idea what could cause this. The apartment is built with concrete blocks.
According to the Technical Data Sheet for Lanco Urethanizer (direct link to PDF), or at least from the way I'm reading it, "Lanco Urethanizer" is meant for external applications where you need to make a surface waterproof.
Therefore if those tenants have used it internally to paint walls & ceilings, they have sealed those services ie Made them waterproof.
If I have the above correct, I believe that would explain why you're seeing condensation on the ceiling (and probably on the walls, especially higher up the walls) ie Moisture in the room can't penetrate the waterproof surfaces, instead it just sits on the surface as condensation.