When you can’t sleep on your first night in a new place, your brain is trying to protect you. Many animals sleep with only half their brain, while the other half stays alert to possible dangers.
It’s called the ‘first night effect’ in humans, because when we sleep in a new, unfamiliar place, our bodies put us in a strange, half-asleep/half-awake state, to protect us from potential danger. Luckily, this usually only lasts one night, after which we can sleep normally.