What is the ruling on being alone with a non-mahram in a closed room whose door closes automatically, and which has a transparent glass window through which those inside and outside can be seen, and what is the expiation for that?

Privacy between a man and a woman who are not mahram (marriageable kin) is forbidden, based on the Prophet’s (peace be upon him) saying: "A man must not be alone with a woman unless there is a mahram with her." Its meaning is the gathering of a man and a woman in a place where they feel safe from anyone entering upon them. If forbidden privacy occurs, its expiation is sincere repentance.