Do Hag's traps trigger even when the survivor is on another level?

I believe the trap radius is spherical. Meaning that in order to trigger it from above or below, you would need to be within the same distance, vertically, as you would need to be to trigger the trap if you were walking next to it. Like if the trap's radius was 6 metres, you could trigger it from walking towards it from 6 metres away, but you could also trigger it by standing on a platform 6 metres below it.

So for example, if the survivor were on the top level of the Ironworks of Misery building and the trap were on the floor at the bottom, they wouldn't trigger it even if they're directly above it, because they're too high up. But if they dropped down onto it, the trap would be triggered before the survivor reached the ground, as soon as they enter the trap's radius.

Hopefully that explanation makes sense - let me know if you have any questions.